Evaluating Martin's claims was difficult, "given his mental health issues, his possible heightened sensitivity to insults and his unusual, 'bipolar' friendship with Incognito," the report said.
"Nonetheless, we ultimately concluded that Martin was indeed harassed by Incognito, who can fairly be described as the main instigator."
The report comes about three months after the league hired Wells to investigate the case, which prompted a national debate about hazing and workplace bullying.
"To a great extent, Incognito dictated the culture," the report said. "We doubt that matters would have gotten so out of hand had Incognito not set a tone on the offensive line that made extremely vulgar taunting a typical form of communication."
Dolphins offensive line coach Jim Turner didn't attempt to stop the behavior and even took part in some of the taunting of "Player A," the report said. Several people interviewed told investigators that Turner gave Player A, a male sex doll as a gag gift around Christmas 2012. Turner told investigators he did not remember the incident, but investigators said they did not believe him.
However, the report found no evidence that the Dolphins front office or head coach Joe Philbin was aware of the conduct Martin found abusive.
The 6-foot-5, 312-pound Martin abruptly left the team Oct. 28. He was briefly hospitalized and then joined his family in California and underwent counseling for emotional issues. Incognito was barred from the season's last eight games.
Incognito expressed regrets about the racist and profane language he used with Martin, but said it stemmed from a culture of locker-room "brotherhood," not bullying.
Martin has said he tried to be friends with Incognito. The two players traded more than a thousand text messages in a year's span, and the teasing and vulgar banter went both ways. Martin also participated in the teasing of Player A, although investigators say he was simply trying to fit in with the other linemen.
The report also mentioned Martin having suicidal thoughts.
"Whether or not Incognito, Jerry and Pouncey fully appreciated the effect of their actions on Martin, there is no doubt that, from Martin's perspective, their actions were abusive and hurtful," the report said. "We are not, however, in a position to evaluate Martin's assertion that the abusive conduct of his teammates was, in fact, the exclusive triggering cause of his depression and contemplation of suicide."
The NFL Players Association said it will review the findings closely, confer with players and all relevant parties involved.
Dolphins owner Stephen Ross said in a statement: "As an organization, we are committed to a culture of team-first accountability and respect for one another."