The Addicks found themselves 2-0 up just before the break when Danny Shittu put through his own net from a Lloyd Sam cross.
However, Aidy Boothroyd's Watford clawed themselves back into the game after half-time.
John-Joe O'Toole started the revival, finishing from close range after some poor defending by the home side.
One minute Danny Shittu made amends for his error in the first-half by thumping home a header to level the scores.
The result leaves Watford equal on points with leaders Stoke, but in second place due to goal difference.
Elsewhere, Leicester were the days big winners, smashing four past Norwich without reply.
Iain Hume put the Foxes ahead after 22 minutes with a neat finish from Steve Howard's lay-off.
The lead was doubled 10 minutes after the restart through Howard himself. The former Derby striker finished from close range after a pass from Patrick Kisnorbo.
DJ Campbell added a third and the win was sealed when Stephen Clemence drilled home past Norwich's David Marshall.
In the other two games played in the Coca-Cola Championship on Saturday, Hull City were held to a 1-1 draw by strugglers Colchester, and Ipswich ran out 2-1 winners at home to Blackpool.