The 41-year-old man was arrested at Killkern Court on De Villiers street in the CBD on Sunday, Warrant officer Xoli Mbele said.
The 36-year-old woman was doing housework when her ex-boyfriend came to her room.
“He argued with her about not answering her phone. She told him that her phone was broken and he threatened to shoot her,” Mbele said.
The man then allegedly poured a litre of petrol over her, set it alight, and fled the scene.
The woman screamed for help and her roommate and neighbours came to her rescue.
They poured water over her and managed to extinguish the fire. She sustained injuries on her right leg.
The woman was not taken to hospital as she sustained only minor injuries, Mbele said.
The man was apprehended by security officers at the flat, who called police.
He was expected to appear in the Johannesburg Magistrate’s Court on a charge of attempted murder.