The son of former Zimbabwe batsman Andy Waller and a talented all-round sportsman, Malcolm attended the well-known Lilfordia School and captained Zimbabwe at every age group level. He seemed destined to follow in his father's footsteps, but that process was delayed after he spent his final years of school in England, where he tried unsuccessfully to secure a professional contract. He returned home in 2004 but flattered to deceive, until good club form finally earned him a national call-up for the tour of Bangladesh in 2008-09. Strong showings for the Mid West Rhinos in the new franchise system led to scattered appearances in international cricket over the next two years, before he finally consolidated a place in the Zimbabwe side in 2011. His 99 not out off 74 balls against New Zealand in November 2011 saw Zimbabwe achieve their highest ever chase in a one-day international, and led to a Test debut for Waller the following week, where he acquitted himself well. Although Waller was a successful legspinner during his school years, he has changed to offspin and become more of a part-timer. As a tall right-hander he carries an air of confidence bordering on cockiness, and displays unusual wristiness for a Zimbabwean batsman.