Ianevski was born in Bulgaria and has also lived in Israel and England, where he was known for his athletic skills. While attending Mill Hill School in England, Ianveski had no particular acting aspirations and was not a drama student. He had only auditioned for Potter after being spotted by Fiona Weir, a casting director who prompted him to attend an acting workshop, which resulted in his casting as Viktor Krum, a Bulgarian character in the Harry Potter series. He was selected from 600 others, most of whom had auditioned in Sofia, Bulgaria.

Ianevski's casting was announced in June 2004. During filming, he befriended fellow Potter actors Robert Pattinson and Emma Watson, who has referred to him as "very sweet". Ianevski also stars in the sequel to Eli Roth's Hostel, Hostel 2.

Ianevski has a sister and several pets. He is a follower of the Bulgarian national football team.