William "Will" D. Tippin is best friend and companion of Sydney Bristow. He was initially unaware of her undercover life with SD-6 and the CIA. He worked for a newspaper until he was kidnapped by Sark, forcing Sydney to save him and expose her real life. Afterward, he was hired as an analyst with the CIA. When his life was threatened, he entered the Witness Protection Program.
Will was shocked when Sydney told him that she was marrying Danny, but was there for her when he was killed (by SD-6 agents because of his knowledge of their existence). After Sydney was targeted by SD-6, seen as a threat herself, she contacted Will for help and asked for his sister, Amy's, credit card and her passport. He managed to get them for her, but he was dubious of why she wanted them. Will asked Sydney why she used his sister's passport and credit card, but she said that she could not tell him. He assumed that Danny was in some kind of trouble, but she told him to forget about it and to trust her .
Jenny, a coworker at the paper where Will worked, asked him out on a date. He said she was too young for him and brushed off the suggestion. He asked her to get the file on Danny Hecht, deciding to ignore Sydney's advice and look into her fiancée's death. He discovered that Danny was booked on a flight to Singapore the night of his death. He told her but she had an excuse.
Later on he is captured by Julian Sark and interrogated for information about the Circumference which he does not know about. He is rescued by Sydney and Jack and is told all about SD-6 and the C.I.A.
Season 2 starts with Will Tippin using a the cover story that he is a drug addict to discredit his previous statements and inquires about SD6. He later becomes an analyst for the C.I.A. and begins a relationship with Allison Doren who he thinks is Francie. Allison hypnotizes him several times in order to get information to Sark. Near the end of the season he is accused of being the other Project Helix 'duplicate' and is brought into custody when in reality Allison is the other clone, having used her earlier to conditioning to ensure that he would have trouble remembering even personal details of his own life so as to increase the idea that he was the mole. He is let out of custody and then figures out that it has been Allison all along. Allison stabs him and puts him in a bathtub presumably dead; although he survives, he is forced to go through the witness protection program as his life was in jeopardy.
His survival was confirmed in the beginning of the season. In episode 10, Sydney has a dream involving Will and contacts him from inside the protection program. He speaks with his contact who turns out to be Julian Sark's father. Later while he is helping Sydney obtain a Rambaldi artifact he kills Allison Doren in an act of vengeance and self defense. He says goodbye to Sydney and promises her that he will see her again (Remnants).
He is mentioned a few times but does not make an appearance in any of the episodes.
Will was later injected with a bomb in his neck by Anna Espinosa. Sydney saved him and he asked her to be the best man at his wedding. Will and Sydney walk through a park where Syd apologizes for the chaos she's brought him. Will assures her that it is not her fault evil people exist, and he sleeps better knowing there is only one Sydney who can keep the world safe. Little did either of them realize that Sydney's long-term nemesis was being genetically altered to look like Sydney (There's Only One Sydney Bristow).
- Amy Tippin - Sister
- Francie Calfo (deceased)
- Allison Doren - as Francie's double (deceased)
- Sydney Bristow
- Unnamed Painter (referenced in seasons three and five)
- The painter referred to by Tippin firstly in season three is never seen nor named, in his recurrence during season five he mentions his plans to marry her.
- He was once named Jonah in season 3.