Garrus Vakarian is a romanceable character in the Mass Effect trilogy, but only starting with Mass Effect 2 and for a female Commander Shepard. Additionally, players can also continue a romantic relationship with Garrus in Mass Effect 3, but only if he was wooed in the second game.
Commander Shepard first meets Garrus Vakarian in Mass Effect 1, but he's not a romantic option alongside Liara, Kaidan, and Ashley until the following game. Still, Shepard will take him aboard the Normandy and can build a rapport with Garrus in the first game, setting up their strong relationship in the second if Shepard recruits the Archangel at the beginning of Mass Effect 2. While the Turian has a loyalty mission in Mass Effect 1 involving Dr. Saleon, it won't negatively impact following games if Shepard doesn't complete it or makes certain decisions during the quest.
How to Romance Garrus Vakarian in Mass Effect 2
Garrus can only become a potential romance option for Shepard after she's completing his loyalty mission in Mass Effect 2. Much like his mission in Mass Effect 1, Garrus is looking to bring someone to justice through vengeance. After finishing the mission with Sidonis, Shepard can start to flirt with him when chatting down in the Main Battery, and Garrus's demeanor will change from his normal calm and collected self into a more awkward persona.
After the initial conversation following Garrus's loyalty mission, continue to talk with Garrus between quests and flirt with him by choosing the obvious dialogue options. Doing so will lead to a sweet, romantic scene in Shepard's cabin while going through the Omega 4 Relay. If Shepard has been romancing either Thane or Jacob in addition to Garrus, when Garrus brings it up, choose "I don't want other options" to continue a romantic relationship with the Turian. This will effectively lock Garrus in. If this scene doesn't occur, pick "I feel the same way" during the third flirty conversation with Garrus to lock him in, leading to the scene in Shepard's room.
If players want to romance Garrus in Mass Effect 3, they'll have to keep him alive through the suicide mission in Mass Effect 2. If Garrus is loyal, assign him for the lead of the Second Fireteams during the Collector Base infiltration. If he's not loyal, avoid assigning him to a specified role or to Shepard's squad.
During Mass Effect 3, Shepard will meet Garrus once again during the mission Priority: Palaven where he'll join the Commander's squad once again. Talk with him after this mission in his usual spot at the Main Battery and pick the dialogue option "I'm still interested." To lock in the romance, after speaking with Garrus multiple times, meet with him at the Normandy Dock: Bay D24 and pick the "Yes. I love you" option to lock him in again.
Mass Effect: Legendary Edition is out now for PC, PS4, and Xbox One.