Mo Johnson emigrated from Scotland to Australia at age 25 after marrying an Australian who she met while working as a teacher in Japan. After arriving in the country she taught English in Sydney up until December 2008.

Johnson's career as an author initially began in 1997 when her husband's work required a temporary move to Darwin (Northern Territory). Being isolated she turned to writing as a hobby and subsequently had two stories published. A return to teaching resulted in almost a decade gap, before she began work on her first novel in 2005. Something More was eventually published in 2009. Her other novels include Boofheads (2008), and the picture book, Noah’s Garden (2010). Several books and articles have been published by the Education press, with others appearing in the US Chicken Soup for the Soul series. A short story, Red Rhino, also appears in the Ford St Press anthology Trust Me Too (2012).