The former NFL linebacker turned bouncer was convicted of killing Bill McLaughlin, the 55-year-old millionaire boyfriend of Naposki's former lover, Nanette Johnston.
The verdict comes almost 17 years after McLaughlin was shot to death in his Newport Beach home.
The verdict is relief for the victim's family.
"We very much miss our father and we're very sad over his loss," said daughter Jenny McLaughlin. "We're very happy that justice has been served on his behalf."
"And also for the 15 jurors who gave 15 days of their life and took this as a huge responsibility," said daughter Kim McLaughlin. "We're very grateful to them, and justice prevailed and we're so grateful.
It took jurors seven hours of deliberations. Naposki shook his head when the verdict was read.
According to a member of the Orange County District Attorney's Office who was sitting near Naposki, at one point he turned to his fiancé and said "don't worry babe anyone can make mistakes, including those 12 jurors."
McLaughlin, a millionaire business man, was shot in his home in 1994. His son had to call 911.
Authorities arrested Naposki and Johnston in 2009 after a cold case investigation was re-opened. The prosecutors said the motive was money. Johnston stood to gain $1 million in life insurance from McLaughlin's death. She is also charged with murder.
Authorities suspected that Johnston convinced Naposki to kill McLaughlin by providing a key to the home that she shared with the victim.
The defense argued that Naposki didn't have enough time to kill McLaughlin, and said it made more sense that Johnston killed him.
But the jury disagreed, and found Naposki guilty of murder for financial gain.
"Eric Naposki is guilty of this," said prosecutor Matt Murphy. "This jury found the evidence was compelling. They convicted him and we got one more defendant to go on this thing."
Johnston's trial is set for Nov. 4.