The veteran midfielder was not involved in Thursday's thrashing of Indonesia All Stars and had earlier in pre-season been struggling with an Achilles injury.
But Lampard, along with fellow absentees Andre Schurrle and Kevin de Bruyne, who has been given the all clear after scans on his knee problem having returned to England at the beginning of this week, will return to training.
The news is a boost for Chelsea as they flew back to London from their tour of the Far East shortly after the 8-1 win over the All Stars ahead of the USA leg of their pre-season.
"Lampard is okay to train Monday, so Monday he will join the group," said Mourinho.
"We protect every little situation and today we protected Schurrle, we sent De Bruyne home, but Lampard preferred to stay and have treatment here with the group."
David Luiz, Oscar, Juan Mata, Fernando Torres and John Obi Mikel, who were excused from the Asia tour following the Confederations Cup, will also rejoin Chelsea for their USA leg.
Mourinho will also hope for more of the same from captain John Terry after he continued an excellent pre-season with a goal in the demolition of the All Stars.
"Terry played well and trained very well and never missed one minute of any training session, and that is very important, because we trained very hard for 15 days and some of the days for two sessions," said the Chelsea boss.
"Every 45 minutes he played, he played well and I am very happy with him."