Ferrier began kart racing in 1993 and moved into Formula Ford in 1998, experiencing mixed results before switching direction. In 2001 and 2002 she raced in Development V8 Supercars, competing for Garry Rogers Motorsport and Fleetcare Racing respectively. The following three seasons saw her turn to Improved Production racing, driving her father Mark's Mazda RX-7 and winning the Victorian and New South Wales championships in 2005. She also raced in the Australian Production Car Championship in 2004 for Team Toyota Australia, adding to the breadth of her early career profile.
In 2005, Ferrier had her first experience in a Formula Three car, contesting three rounds. She committed to the Australian Formula Three Championship full-time in 2006 and, in 2007, became the first female driver to win a race in the series. Her 2007 championship campaign was particularly strong: after scoring a pair of second-place finishes at Symmons Plains Raceway at the penultimate round, she entered the finale at Oran Park Raceway leading the championship by four points. She qualified on pole position for both final races and finished third and second respectively — just not enough, as the title escaped her by two points. This result remains the best achieved by a female driver in a national Australian circuit-racing championship and is considered among the finest performances by a woman in any national or international Formula Three series.
In 2008, Ferrier stayed in Australian F3 and claimed four pole positions and five race wins but again narrowly missed the championship, losing to James Winslow in the final round.
In 2009, Ferrier joined Paul Cruikshank Racing for the V8 Supercar Series and also returned to the Super2 Series in a TanderSport-prepared Ford Falcon BF. In 2010 she competed in the Touring Car Masters driving a replica Ford Falcon XA GTHO Phase IV, finishing fifth in the series overall and winning the last race of Round 5 held at the Mount Panorama Circuit during the support programme for the 2010 Bathurst 1000.
In 2007, while Garth Tander led the Supercars Championship and Leanne led the Australian Drivers Championship at points during the season, the couple became the first married pair to have simultaneously led Australian motor racing championships — a unique intersection of two careers at the top of their respective disciplines.
Ferrier married Australian racing driver Garth Tander in 2004 and raced under his surname from 2005 onwards. The couple separated in 2022, after which she resumed use of her birth name, Ferrier. They have two children together, a son named Sebastian and a daughter named Scarlett. As of 2012, Ferrier has also contributed to the entertainment and lifestyle website Live4.