Many of the passengers were university students, Homs Governor Talal Barazi told state-run Ikhbariya television. The blast hit the Akrama neighbourhood, near al-Baath university.
Footage showed people crowding around a burned vehicle in the middle of a street.
"A bomb that terrorists planted in a passenger bus exploded," state TV said. Eight people died, it cited the city's health authority as saying.
Islamic State claimed responsibility for a similar attack in Homs in May, when a car bomb killed four people and injured 32 others. A string of bombings have struck cities under government control across Syria this year.
The city of Homs went back under full government control in May, for the first time since the onset of Syria's conflict more than six years ago.
Hundreds of Syrian rebels and their families left the city's last opposition district, al-Waer, which the army and allied forces had besieged.