She is in the Eastern European country with her husband Ryan Sutter, and their son Maxwell, 9, and daughter Blakesley, 8. Trista met Ryan on the show.
Trista, 44, shared the news via an Instagram post, which included a photo of herself lying in a hospital bed in Croatia, with an IV visible and patches on her chest.
She did not elaborate about the seizure nor did she offer any insight into her health.
"This was me yesterday....two hours after I had a seizure....two hours after I fell on my daughter's chest & she watched, along with her brother & grandparents, in confusion & horror as her mommy stared blankly off into the distance & started turning blue. ...two hours after we were supposed to have an adventure. An adventure to one of the most beautiful National Parks in Europe," she wrote.
She further explains, "Instead, I ended up in a euphoric white dream that the voices of my husband and daughter pulled me from and I ended up in a Croatian hospital being poked and prodded and wondering 'why me?' But today, I had to ask, 'why not me?' I'm human."
Trista also appears to question her own mortality, writing, "I have an expiration date. I've always envisioned that date being sometime after my kids have graduated college, met the loves of their lives and created families of their own, but I was reminded yesterday that it could come anytime, in any country, whether I'm surrounded by strangers or people I love, or neither, or both."
The seizure seems to have made her introspective and re-assess her life.
"I've never been perfect and I never will be, but from here on out, I vow to try my best to live this life to the fullest," she writes. "To embrace gratitude and the lessons I wrote about over 3 years ago with a newly acquired perspective. To stress less. To love more. To listen. Be kind. Spread joy. To be a better version of myself as a wife, mother, sister, cousin, niece, aunt, neighbor, daughter, and friend."
The frightening episode also appears to have made Trista appreciate those around her even more, as well as fans and strangers she's met.
"Thank you to those back in the states, whom I hold dear. You know who you are," she writes. "Thank you to those I've never met who lift me up and have my back. Thank you to those from my #bachelornation family who've shown this OG kindness & respect when I know I'm old news. Thank you to the kind tourists & Croatians who held my hand, wiped my tears, and hugged my kids. You will forever be remembered."