Police say that shortly before 4.30 pm yesterday, a man approached the lady in Cavendish Square and tried to take her car keys from her.
The elderly woman tried to stop him taking the keys but was then assaulted before the thug made off empty handed.
Not long afterwards, a second attempt was made to hijack a van on the Falls Road, in which a man was also assaulted.
The thug failed to get the keys off the driver but was struck by a passing white coloured car.
A 24-year-old man was later arrested by police and is being questioned.
The van driver and the elderly lady were both left badly shaken by the incidents, with the lady suffering bad bruising.
Police in west Belfast have appealed for anyone with information to contact them on the 101 non-emergency number.