Simon Cox looked to have marked his first Forest start with the winner at the John Smith's Stadium, but Rhodes had the final say.
The Scotland striker barely touched the ball all evening at the John Smith's Stadium, but he showed why he is so highly sought after by keeping his cool to slot home from the spot three minutes into time added on after Dan Harding had brought down Jack Hunt.
It looked like the Terriers' first home game in the Championship after an 11-year absence from the second tier would end defeat after Cox, a recent £2million signing from West Brom, struck midway through the second half.
But Simon Grayson's side were not to be denied and Rhodes held his nerve to beat Lee Camp. Forest will feel hard done by as Lewis McGugan and Cox were both denied by the woodwork in the first half.
But Huddersfield also had their chances in a open encounter in West Yorkshire and they are up and running after a defeat to Cardiff last Friday.
Forest played with a swagger right from the kick-off and they were unfortunate not to be in front after just three minutes, when McGugan's long-range drive rattled the post.
Huddersfield started nervously and left-back Paul Dixon's sloppy backpass should have been punished by Dexter Blackstock, who shot straight at the advancing Alex Smithies.
Sean Scannell was a dangerous outlet for the Terriers and the summer signing from Crystal Palace fired a shot over the crossbar 14 minutes in.
And Huddersfield should have been in front six minutes later when Adam Clayton picked out Lee Novak with a pinpoint pass, but the striker fired wildly over the crossbar.
Forest looked dangerous every time they came forward and Huddersfield almost gifted them the opening goal when Scannell's wild attempted clearance went straight up in the air and Blackstock headed on for Cox, whose close-range finish was well blocked by Smithies.
The visitors came close once again after 25 minutes when midfielder Adlene Guedioura controlled the ball on his chest and swivelled before unleashing a vicious right-footed volley which Smithies palmed over the bar.
Forest were dictating the game and Brendan Moloney raced away down the right before cutting the ball back for an unmarked Blackstock, whose shot was cleared off the line by Jack Smith and, when the ball fell nicely for Cox, his shot was palmed onto the bar by Smithies.
The Terriers had the first chance of the second half, but Keith Southern prodded the ball over the bar when Oliver Norwood's corner fell nicely for him eight yards out.
And he was made to pay for that miss when Forest took the lead in the 68th minute when the impressive McGugan played in Cox and the Republic of Ireland striker raced away and beat Smithies with a clinical left-footed finish.
But Hunt charged into the penalty area with time running out and drew the tackle from Harding and, after referee Neil Swarbrick awarded a penalty, Rhodes picked his spot to rescue a point.