The 38-year-old comedian had been scheduled to perform at the Derby Assembly Rooms on Friday night, but made the decision to postpone the event in order to be with his family.
Russell took to Twitter to apologise to fans, explaining, "My mum ain't well".
He later expanded on the reason during his YouTube show The Trews.
"My mother has currently got breast cancer," he said in his video blog, while speaking of his dismay that the NHS is "being destroyed" by cuts.
Barbara, who has a very strong bond with her son, successfully battled uterus cancer when Russell was eight, and breast cancer a year later.
Russell often pays tribute to her for her bravery and love, in no small part because his parents split when he was just six-months-old and she raised him as a single parent.
It remains to be seen whether Russell will continue with his scheduled Messiah Complex shows in Plymouth and London this weekend.