The fixtures will follow the club's two-game tour of Iceland and features two games against Premiership opposition, including Alan McLeary's long-awaited testimonal against Charlton Athletic.
The full fixture list is as follows:
Saturday 15th July
Crawley Town v Millwall (Kick-Off 3pm at the Broadfield Stadium)
Saturday 22nd July
Millwall v Charlton Athletic (Kick-Off 3pm at The Den (Testimonial for Alan McLeary))
Wednesday 26th July
Millwall v Reading (Kick-Off 7.45pm at The Den)
Saturday 29th July
Millwall v Crystal Palace (Kick-Off 3pm at The Den)