Marotta oversaw great success during his Juve tenure, wining included seven consecutive Serie A titles and making two UEFA Champions League final appearances, before leaving the club in October.
The 61-year-old, who also had a spell at Sampdoria, has already described his move to Inter as 'an important chapter' in his career and professional life.
"I am now part of the great Inter," Marotta said on Thursday.
"I'm very proud and I'm going to have the important role of the CEO of the sports area. It is certainly going to be an important chapter in my professional life and I will have great responsibility, but that doesn't daunt me.
"It's the start of a new chapter and it must be one marked by success."
Inter will hope that Marotta can help guide the club back to its former glories after going seven years without a trophy. That came in the shape of the Coppa Italia in 2011, while Inter haven't won Serie A or the UEFA Champions League since Jose Mourinho's remarkable treble in 2010.
The club crashed out of the Champions League at the group stage this week - their first time in the competition since the 2011/12 campaign - and will continue their continental adventure this season in the Europa League in the new year.