He was investigating and exposing human rights violations in Rwanda and activists had called for investigations into his death.
The motorist who pleaded guilty will also pay $500 for injuries to the motorcyclist who was carrying Ntwali.
The prosecution during the trial had asked the court to jail the motorist for two years and fine him $1,800 after he pleaded guilty and asked for forgiveness.
The law in Rwanda allows 30 days to appeal but Ntwali’s family has told local media they will not file an appeal.
Dozens of African civil society groups and press associations on Tuesday called for an independent investigation into Ntwali’s death, saying the official explanation lacked sufficient evidence.
“Rwandan authorities have failed to provide a police report, the exact location of the alleged accident, any photo or video evidence or detailed information on the others involved in the accident,” the statement said.
Ntwali had previously expressed fears for his life and told the Human Rights Watch rights organization that he had received phone threats and strangers had visited his house. Ntwali had been described as Rwanda’s last independent journalist and lauded for his brave reporting on human rights violations.