David McGoldrick had opened the scoring with his own set-piece special, just moments after Rovers’ defender Matthew Kilgallon had been sent off.
McGoldrick had two great chances to make the points safe but Marshall’s late free-kick was perfectly placed to send the travelling Blackburn fans home happy.
In a cagey opening, Jordan Rhodes came close to latching onto Marshall’s cross before Lee Williamson’s volley from the edge of the area was deflected wide.
Ipswich took time to show why they had gone seven games unbeaten with Jonathan Parr spurning a good chance from a volley after good work from fellow full-back Tyrone Mings.
Blackburn went close on 23 minutes when Rudy Gestede rose highest at the back post but he headed Craig Noone’s cross wide.
The visitors continued to carve out the game’s best moments – Dean Gerken saving Rhodes’ header and Shane Duffy just failing to grasp the rebound.
The best Town could muster was a 33rd-minute free kick from McGoldrick which was smartly held by Jason Steele under pressure.
The deadlock was almost broken nine minutes before the interval when Gestede turned Tommy Smith inside out but his low near-post shot was palmed away by Gerken.
Moments later it was the turn of Blackburn keeper Steele who flung himself to his right to beat out a great curling shot from McGoldrick.
Within two minutes of the restart, McGoldrick had streaked clear of the Blackburn backline but his low cross was well held by the diving Steele as Stephen Hunt waited to pounce.
The Town striker then saw a free-kick whistle just wide of the far post after Conor Sammon was cynically hacked down by Matthew Kilgallon.
The centre-back was perhaps fortunate to only see a yellow card, but when the two players clashed again in the 66th minute, Killgallon was given his marching orders.
And Blackburn’s misery was complete when McGoldrick curled the resulting free-kick brilliantly into the corner.
Ipswich almost doubled their advantage soon after when Hunt’s downward header was cleared off the line by Shane Duffy.
McGoldrick was denied a deserved second in the 81st minute when he met Kevin Bru’s teasing cross with a first-time volley that smacked the near post.
McGoldrick was the dangerman and he broke clear with two minutes left on the clock but his effort was pushed away by Steele.
Then, against the run of play, Marshall curled home the game’s second stunning free-kick to give Blackburn a point.