The actor, 67, had nothing but loving words on Thursday when he shared the trailer to her film, Off the Rails, on his Instagram account.
"Off the Rails is Kelly's last film," he wrote in the caption. "She was very proud of it and of all of the wonderful talent that she got to work with in it."
Also starring Jenny Seagrove and Sally Phillips, Off the Rails follows three women as they recreate an inter-rail journey across Europe from their youth in honor of their late friend, whose last wish was that they go on the trip with her teenage daughter in her absence.
The film hit theaters in the United Kingdom and Ireland on Friday.
In the comments section of Travolta's post, the actor's 21-year-old daughter with Preston, Ella, responded with three red heart emojis.
Preston died on July 12, 2020 following a private two-year struggle with breast cancer. She was 57.
Travolta and Preston were married for 28 years before her death, after tying the knot in 1991.
The Face/Off star has spent the past year grieving the loss of his wife in private, working through this "personal journey." Travolta said in a profile with Esquire Mexico this April that healing has been complicated and the outpouring of support hasn't exactly been helpful.
"The most important thing you can do to help another person when they are in mourning is allow them to live through it and not complicate it with yours," he told the publication. "Even though it's great to have company, sometimes it turns into you helping them instead of you working on your loss and grief."
"You have no idea how many people have come up to me … and afterward I've felt saturated with everyone else's pain that I didn't know what to do," Travolta continued, noting that he still appreciates the condolences. "The first thing you should do while going through grief is go somewhere where you can truly mourn, with no interruptions."
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Travolta shared a heartfelt tribute to Preston this May in honor of Mother's Day, posting throwback pictures of the couple with Ella and sons Benjamin, now 10, and Jett, who died in 2009 after suffering a seizure at the age of 16
"Dearest Kelly, you brought into my life three of the most wonderful children I have ever known. Thank you," he wrote on his Instagram. "We love and miss you. Happy Mother's Day."