Sara Lance much like Oliver, is a person who "just couldn't stay out of trouble". As the younger of two siblings, Sara was something of a "black sheep" to Laurel Lance's "golden child". She made unwise, often selfish decisions, such as pursuing a boy with a girlfriend while in high school, provoking physical attacks from his girlfriend and her friends in retaliation. She apparently got in a fair bit of trouble as a teenager, including one incident of shoplifting that her father made go away. She also had an affair with her sister's boyfriend Oliver, suggesting that loyalty to her sister meant nothing to her.

Though this may have something to do with the fact that she had a crush on Oliver before he started dating Laurel, which Laurel knew about and possibly sabotaged by informing her father about the party and the fact that Sara was there. In her youth she snuck out of her house to spend alone time with Oliver. Going on the Queen's Gambit was her way of getting revenge for what Laurel did to her. The fact she was with Oliver led to her presumed death when the Queen's Gambit went down.

However in her time spent with Dr. Anthony Ivo after being rescued by him, Sara appeared to become more apathetic, cold and brutal, more savvy with technology and science, even helping Ivo torture his test subjects, though secretly she was terrified of being the next subject so she kept to herself. Despite Oliver being one of the reasons for her shipwreck, Sara still cared about him, so that when he is captured on the boat she does everything to stop the crew from killing him, though she was still loyal to Ivo. She used Oliver to obtain Shado and Slade Wilson's location on the island though her loyalty was shattered when Ivo called her an "ungrateful bitch" on the radio. After spending time with Oliver and Slade she also regained her sense of loyalty.

Soon after she was recruited into the League of Assassins and became a cold killer, though she never forgot her family and still cared deeply for them, but had become afraid to reveal the fact that she was alive to her family, fearing that they'll reject what she had become.

Becoming the vigilante 'the Canary', like Oliver, Sara has displayed a sense of honor as well as guilt and remorse for her actions. She labels herself a murderer for one particular assassination where she killed a beloved father which lead to her leaving the League. Nevertheless, Sara has displayed a vengeful nature, perfectly willing to kill people who have harmed those she holds dear such as Barton Mathis, Xavier Reed and Helena Bertinelli, the latter two she only didn't terminate because two people close to her convinced her not to kill them.

Sara also still deeply loves Oliver, even 6 years after the Gambit's sinking and the events of the island, and was even in a relationship with him again, even though their affair was what destroyed Oliver's relationship with Laurel in the first place. She also loves Nyssa despite the violent causes she serves, to the point where she refused to kill Nyssa and begged Oliver not to kill her when he had the chance. She cares for wayward orphan Sin like a little sister, partially because of a promise she made to Sin's father before his death on the island. Becoming a member of Oliver Queen's team, Sara got along well with John Diggle and like Felicity uses his nickname "Dig". She also got along well with Felicity Smoak and was actually amused by her awkwardness, telling her she thinks it's cute.

Sara did not get along so well with Roy Harper, mainly due to his Mirakuru injected rage, even willing to kill him with an arrow when he lost it at John, and again later when he hurt Sin and endangered Thea. However, Sara came to regret these actions of hers, as her reasons for wanting to kill Roy were not justified. Caring for Oliver, she comes to the conclusion a killer is what she is because that's what the League made her be, so ends her relationship with him because she cares about him too much to be with him. Sara describes herself on this matter as being lost in the shadows and did not believe she can come back from it.

In "Streets of Fire", when Laurel told Sara she knew who she was, Sara told her sister she was the farthest thing from a hero. Laurel humored her sister as well as comforted her in that while she wouldn't pretend she'd experienced anything she had, she couldn't be called the Canary if she was so irredeemable. Sara found comfort in that she was praised as a hero saving a child from a burning building. She starts adjusting to and accepting this new mindset joining Oliver in taking down Werner Zytle and preventing his bombing without killing or attempting to kill anyone involved.