The outgoing Newcastle United manager was in the stands at Villa Park to cast an eye on his prospective new side, who were held to their second consecutive 0-0 draw in the Premier League by Aston Villa.
Yannick Bolasie spurned the best opportunity of the game, thrashing a first-half strike against the crossbar, with the result ensuring Palace remain in the relegation zone.
Attention will now switch to the FA Cup this weekend, with interim boss Millen claiming Pardew will lead preparations for the third-round tie against Conference side Dover Athletic.
"We are preparing for Alan to come in tomorrow to start working," he said.
"I kept the lads in the know from what I knew from the chairman. Before the game when we left the hotel we weren't sure but then I got a message to say Alan was coming."
It will be the first opportunity for the former West Ham boss to stamp his authority on the team, with plans for the future already in place as Palace look to retain their Premier League status.
Millen added: "He didn't have any input during the game or before it, but he came in after and was pleased and proud with what he saw.
"He said we need to add more to our game to score more goals and win football matches but it's a good start for Alan to see us.
"Hopefully he can improve the team and make us better."
‘He instantly popped into our ratings as one of the best U21 midfielders in Europe. The impressive thing is Slot has made him into more of a no.6' Inside Ryan Gravenberch's transformation at Liverpool
‘I don’t think Liverpool would look at Ollie Watkins, a striker isn’t a pressing issue for them – it’s Arsenal who need one’ Former Reds star explains why his old club don’t need an out-and-out forward this summer
