- -"Good evening, Miss Sullivan. I am sorry for the cloak-and-dagger routine, but I didn't have time to schedule this little meet and greet. My name is...".
- -"You can save the introduction. I know who you are. And I don't care to talk with anyone connected to Lex Luthor".
- Chloe Sullivan and Tess Mercer, Instinct.
Chloe Sullivan and Tess Mercer began to interact after Tess had arrived in Smallville, taking possession of the Luthors' legacy following the disappearance of Lex Luthor. From the start, Chloe never trusted Tess, since she saw her as a potential enemy due to her being an ally of the Luthors. However, as time passed, Chloe began to see her that her true allegiances were lying with Clark and his Justice League, leading to their alliance and, eventually, friendship.
After Lex Luthor had disappeared, Tess took possession of all his projects and businesses, including Black Creek, the center for metahumans where Chloe had been moved after being arrested by the DDS. She became aware of all the information regarding Chloe and since then has maintained a great interest in her.
- "You learned well from Lex. When you don't get your way, you just... threaten. This isn't my first tour of duty on the Luthor battlefield so you're gonna have to come at me with a lot more firepower." Chloe Sullivan to Tess Mercer, Instinct.
The first time they met, Tess was snooping around the Talon for Chloe, because she knew that Chloe's new power could help her to unravel the mystery behind a strange super-computer that she found in the Arctic Circle. She tried to convince Chloe to work for her, saying that she knew all about her from Lex's records but Chloe refused to be intimidated and told her that she had already faced the Luthors and was used to deal with worse things.
After Tess showed Clark the Crystal of Knowledge, Chloe realized the crystal was the computer system Tess wanted her to hack into. Chloe went to the Luthor Mansion to threaten to press charges for breaking into the Isis Foundation and offered to take a look at the supercomputer but Tess informed her that the crystal was stolen.
Tess suspected Chloe of being the thief. Weeks later, Chloe found the crystal at the Kent Farm and once again met Tess who had gone to the farm because she had traced the signal of the crystal coming from there. Chloe hid the crystal and invented an excuse that made Tess suspect more about what she knew. Tess had the crystal generator that Chloe needed to release Clark and Lois from the Phantom Zone so Chloe recruited Oliver to steal it from Tess.
After Clark began to rely more and more on Tess, Chloe warned him that Tess was very close to discovering his secret and told him to be more careful than ever. Tess organized a human hunt for Chloe and Davis regardless that it would endanger Chloe's life. Tess used this situation to make her shape-shifting assistant pose as Chloe in order to infiltrate Clark's life and learn about his secret.
- "I need to kill you, Tess" - Chloe Sullivan to Tess Mercer, Sacrifice.
Chloe discovered that Tess had filled her cousin's computer with powerful spyware and concluded that she was trying to discover where Lois had been since she disappeared. Chloe began to monitor Tess' movements more closely and then discovered that she had been tracking several Kryptonians around the globe. She tried to find out more about Tess' projects but then bumped into Tess's new boy wonder who prevented her from entering Tess' computer. Chloe managed to convince Stuart to become a double agent working to spy on Tess.
When Tess kidnapped Lois and tried to discover what was behind his memories, Tess discovered that in the foreseeable future, Chloe kills her, and is shocked by this news.
Chloe and Tess confronted each other when the solar tower was near completion. With Chloe aware of what the solar tower was capable of when combined with LuthorCorp technology, she attempted to release a computer virus at the Daily Planet. Tess tried to convince her not to do it by appealing to their joint desire to protect Clark's secret. Chloe refused to believe Tess and a fight ensued. Tess got the upper-hand and almost shot Chloe with the intention to protect herself in the future, as if Chloe was killed in the present, Tess would not be murdered by her in the future. Clark saved Chloe just in time by super-speeding Tess away.
With Clark under the spell of his own persuasion, caused by gemstone kryptonite, he almost killed Tess for vengeance for her killing Jor-El. Despite her dislike for Tess, Chloe intervened just in time to save Clark from himself, as she knew he would not be able to live with himself for killing another person.
Tess continued her distrust of Chloe when she had one of her employees spy on Chloe and Oliver. Tess eventually discovered Chloe's identity as Watchtower through her involvement with Checkmate. They were forced to rely on each other when Clark became infected with red kryptonite and started to reveal his secrets to Zod. As it was in both Chloe and Tess' interest to protect and stop Zod, they teamed up to send Metallo in to stop Clark.
Tess and Chloe were thrown together again when they became trapped in the Watchtower. Realizing that Checkmate was their common enemy, Tess and Chloe had a truce in order to escape the tower and deactivate the GPS tracker that Checkmate had implanted into Tess. Chloe realized that the only way it could be disarmed was to kill Tess. Tess reluctantly agreed and, once the tracker was disarmed, Chloe hesitated before resuscitating Tess. However, her conscience decided to save Tess, which she was very grateful to Chloe for. Chloe insisted that Tess owed her one.
Tess revealed to Oliver that she helped Chloe reset the systems at Watchtower before she left, because Chloe knew that Tess was the only one who could understand how to do it and the only one who could understand why she was doing what she was doing. Oliver then showed Tess a passionate letter he thought she wrote but Tess revealed Chloe did.
Tess began to show some admiration and sympathy for Chloe after she goes missing, saying that they should respect her actions and even confronted Oliver about his decision of tell the world about his secret identity, claiming that what he was doing was not what Chloe would have liked for him.
Tess took over Chloe´s role at the Watchtower at the request of Oliver and Clark, and despite making some modifications to the place, claimed that she did not want to take her place.
Finally, after Chloe returned to the city, she and Tess began to interact more often because they now had friends in common.
Chloe and Tess were both present at Clark and Lois's bachelor/bachelorette party and after things got out of control as everyone at the party drank some champagne that was spiked with magic, Tess and Chloe were later at Watchtower trying to figure out what happened the night before. Tess was popping hangover pills, as her and Chloe began to looking for leads. Tess then asked Chloe if she wanted take over what she was working on, alluding to the work of Chloe on the Watchtower, but Chloe declined, saying "it" was in good hands. After all backs to normal, Chloe, Tess, and everyone at Watchtower watched the assuming footage recorded by Emil from the night before and Chloe leaves again.
While Emil Hamilton was downloading the conscience of Tess into a computer system making her a hologram, Chloe was outside and was waiting for Clark to tell him about her pregnancy. When Clark went outside she immediatly asked him how is Tess.
At Watchtower, Chloe, Tess, Clark and Lois discuss about Earth-2, which was presumably annihilated by the Monitors, and Clark wonders what crime could that Earth have committed to deserve to merit annihilation. Chloe says everything she knows about the alternate Earth and the Monitors but also informs them that the memories, that were transported to her from her doppelgänger never actually took root and she only gets fleeting glimpses. Tess informs them that Lex is preparing his jet to visit Moscow and Lois thinks of a way to sneak in as a press attaché and go to Russia with Lex so she can keep an eye on him. Clark then says he has a better idea and the proceeds to communicate with another member of the team, asking for a favour.
- The relationship between Chloe and Tess is quite similar to that Chloe possessed with both Luthors in the past seasons.
- Tess is the only woman in the series, besides Moira Sullivan, that knows that Chloe was a meteor freak. In fact, she was one of the few people that knows Chloe's secret, being the others Clark, Jimmy, Lex, Lionel and Moira.
- During the Comic-Con in 2008, Cassidy Freeman titillated the audience by saying "she'd like to see her character kiss Chloe".
- Both Chloe and Tess have some attraction towards Clark Kent. 
- Chloe has killed Tess two times. The first time was in Pandora, an alternate future under Zod's rule. The second time in Sacrifice, to save both their lives from Checkmate, later resuscitating her with atropine.
- Lois,Tess and Chloe were the only three women who left their mark on Oliver Queen.
- Chloe and Tess share the same role in Oliver's team of heroes since both were in charge of the Watchtower. Some fans consider Chloe as the original Watchtower and nicknamed Tess as Watchtower II.
- Both Tess and Chloe die saving Lex in some way. In Fracture, Chloe briefly dies resurrecting Lex while Tess is stabbed by Lex in Finale, Part 2, stroking his cheek with a neurotoxin that erased his memories, in essence "saving" Lex from his dark past.
- Chloe and Tess are the only two main female characters to never work at the Talon and resides at the Kent Farm.