After initially signing on loan, the 23-year-old designated player inked a multi-year deal with Atlanta. Terms of the transfer were not disclosed.
Martinez is the leading scorer in MLS with five goals after three weeks of the season. Following a scoreless debut, the Venezuelan striker scored a hat trick at Minnesota United and added a brace against Chicago on Saturday.
“The loan deal had an option to make the transfer permanent which we have now triggered as planned,” Atlanta United president Darren Eales said in a club release. “Josef has been a fantastic addition to our club and it’s clear he has the ability to continuing making an impact in our league.”
During his time with Torino, Martinez scored 13 goals and had six assists in 76 combined appearances after joining the club in 2014.
Martinez is currently with the Venezuela national team for its World Cup qualifying matches taking place from March 23-28. He has been capped 37 times and has scored nine goals since making his debut for his country in 2011.