Five consecutive draws for Wales in group D as Mitrovic’s second half strike cancels Ramsey’s first half penalty.
Wales remain unbeaten in their 2018 World Cup qualifying campaign, but Chris Coleman will feel frustrated after his side let their lead slip for the third time in six games.
Ramsey scored the opener from the penalty spot after Sam Vokes was pulled to the ground by Milivojevic in the Serbian box.
Although Wales secured the advantage going into half time, Mitrovic scored the equaliser after 73 minutes.
Ramsey could have scored again in the second half , Joe Allen threading a pass through the Serbian defence but for the Arsenal man to shoot straight at the Serbian goalkeeper.
After the draw Wales remain third, four points behind group leaders Serbia and the Republic of Ireland who both have 12 points.
Wales will face Austria in their next Group D qualifier at the Cardiff City Stadium on the 2nd of September before they travel to Moldova on the 5th of September