Ahmed Hussein-Suale was near his home Wednesday in the Accra suburb of Madina when two men on a motorbike pulled up next to his car and shot him at close range, according to the lawyer, Kissi Agyebeng.
The journalist died instantly after being shot twice in the chest and in the neck, Agyebeng said.
Ghanaian police have not responded to repeated CNN calls about the killing.
Hussein-Suale worked for the Tiger Eye PI organization run by investigative journalist Anas Aremeyaw Anas.
In a statement, Tiger Eye PI said Hussein-Suale had received death threats after recently finishing work on a documentary that exposed bribery and corruption in African soccer.
The undercover investigation led to the resignation of the head of the Ghana Football Association.
Anas reacted to the news about his colleague's death in a tweet, saying: "Sad news, but we shall not be silenced. Rest in peace, Ahmed."
Agyebeng, the lawyer for Tiger Eye PI, told CNN that Hussein-Suale started to receive threats after a member of Ghana's Parliament exposed the undercover reporter's identity on live television and encouraged viewers to attack him.
The lawmaker, Kennedy Agyapong, showed pictures of Hussein-Suale and revealed the neighborhood where he lived in an interview on TV channel NET 2.
"That boy that's very dangerous, he lives here in Madina. If you meet him somewhere, break his ears," English subtitles on the video quoted the lawmaker as saying.
CNN has not been immediately able to reach the politician for comment.
Agyapong, a member of Ghana's ruling New Patriotic Party, can also be heard in the video offering to pay for anyone who attacks Hussein-Suale.
The lawyer said, "We complained at the time he released the video. He said in the local language he was offering a reward for anyone who would beat him up. He endangered a young man's life, and now this has happened. He has questions to answer."
More about: Ghana