The Swiss champions confirmed the signing of the young Netherlands international from Feyenoord on Tuesday for a fee believed to be in the region of €2.5 million.
Premier League side Newcastle had expressed an interest in signing Boetius earlier this summer and the 21-year-old says he spurned advances from elsewhere in order to make what he considers the best move for his career.
"I didn't had a good feeling any more at Feyenoord," he told Fox Sports. "I needed a challenge. You have to feel that you are valued in the team.
"In pre-season, everybody is very busy so I didn't have a conversation with [head coach] Giovanni Van Bronckhorst. I don't know if it would have mattered. There was interest from different clubs, but this was the best option."
Boetius, who has one cap for the senior Netherlands team, joins Basel as a direct replacement for Paraguay international Derlis Gonzalez, who has joined Dynamo Kiev.