Smart started racing in the latter half of the 1960s after attending the Charles Mortimer Race School at Brands Hatch race circuit, Kent in 1965, initially buying a Bultaco which proved expensive and unreliable, and later riding a variety of machinery in different classes on UK short-circuits.
For 1966 Smart shared a 125 cc Honda with John Button whilst saving money to buy a 250 cc Cotton which he rode successfully at club level, eventually winning the MCN 250 cc Championship. After the Cotton engine failed, he was provided with a Greeves by Chas Mortimer.
During 1967, Smart was sponsored by Charles Mortimer Senior, proprietor of the Charles Mortimer Race School based at Brands Hatch race circuit, Kent, riding from a stable consisting of RDS Greeves 250s, a Bultaco 125 and an Aermacchi 350 together with Chas Mortimer, Charles' son. Both were also employed as road race instructors at the race school.
At the Isle of Man TT Races on a 745 cc Dunstall Dominator for Paul Dunstall, Smart scored second place in 1967, and again second on a Norton Commando in 1969, both in the Production 750 cc class.
Smart moved on to regular successes during 1969 when he was sponsored by Joe Francis Motors, a London motorcycle dealer selling AMC, which provided a 750 cc Norton, a Seeley, a 250 cc Yamaha, and winning the Hutchinson 100 Production machine event on a Triumph 750 cc. For 1970 there was a works Triumph Trident 750 cc and his own 350 cc Yamaha.
In the Transatlantic Trophy Anglo-American Match Races in 1971 Smart rode a Triumph triple and was joint top scorer with Ray Pickrell in the winning UK team. In 1973 and 1974 he captained the UK winning team riding a works Suzuki 750 two-stroke triple.
Smart is remembered for winning the Imola 200 on 23 April 1972, at age 29, riding Ducati's new 750 racer, based on the GT750 roadster. Ducati paid his airfare and £500 wages. His winnings were an additional £6,000. A 750SS road bike and production race version followed, turning into the 1975 900SS which continued until the early 1980s.
In the early 1970s Smart was riding in North America for the Hansen Kawasaki team on air-cooled H2R two-stroke triples. He won what was stated to be the richest prize in motorcycling history – over £12,000 – in a 1972 race at Ontario Motor Speedway, California on a Seeley-framed Kawasaki H2R.
After making history for Ducati and winning further races, in 1978 Smart finally hung up his leathers and retired from competition to concentrate on his motorcycle business, which he expanded into three separate shops at one stage. He sold the shops and the family caravan park business in Kent, later qualifying as an offshore sailing skipper, formalising his long-time hobby.
In 2006, Ducati produced a 1000cc limited-edition PaulSmart 1000 LE, in recognition of the 1972 Imola win, designating it Paul Smart 1000LE. It had the advanced-technology of the time, but resembled the 1972 race bike.
Smart married Barry Sheene’s sister Maggie in 1971. Son Scott is a former Grand Prix racer who won races in the British Superbike Championship then turned to Superstock, and is technical director of World Superbike Championship for the FIM.
- Motor Cycle 9 March 1967. Racing Line by David Dixon. Accessed 20 June 2013
- Motorcycle Mechanics (magazine), October 1970, p.40/41. Interview with Paul Smart by John Robinson. Accessed 9 March 2014
- Motor Cycle 7 July 1966. Road racing reports. Accessed 23 July 2013
- Motor Cycle 15 September 1966. Manx Grand Prix Practicing. Accessed 3 July 2013
- Motor Cycle 8 September 1966. Shell Advertisement - Shell backs the up and comers. Accessed 3 July 2013
- Motor Cycle, 3 August 1967. p.1072/75. 'School for road racers'. "The instructors are now Charles II and Paul Smart, both of whom, rather confusingly, are also under Charles Mortimer I's sponsorship as riders in their own right." Accessed 9 August 2013
-  Official TT race results 1967. Retrieved 21 June 2013.
-  Official TT race results 1969. Retrieved 21 June 2013.
- Motorcycle Mechanics (magazine), October 1970, p.63. Joe Francis Motors Ltd advert "We are 100% AMC" Accessed 9 March 2014
- Motorcycle Mechanics (magazine), October 1970, p.58. Joe Francis Motors advert Brands Hatch 9 Aug Hutchinson 100 Races "Congratulations Paul Smart, 1st Production machine race 750 cc Triumph". Accessed 9 March 2014
- "MotoGP™ Riders". www.motogp.com.
- motorbiketimes.com Retrieved 2013-06-21
- Motorcyclist, May 2007, Pg 132, "The Holy Trinity", Paul Smart compares the original Imola 750 racer, '75 750 Super Sport, and new PS1000 LE SportClassic.
- £12,000 win for Smart. Motorcycle News, 4 October, 1972, p.1 (cover). Retrieved 5 January 2021
- Race of the Century Ashonbikes.com Website of the late Kevin Ash. Archived from the original on 5 February 2013. Retrieved 30 October 2021
- Bike February 1976, p.11, advert Paul Smart Motorcycles Ltd., 100% Honda Specialists, 42/46 Lower Stone Street, Maidstone, Kent. Accessed and added 17 June 2014
-  Genes Reunited. Free online marriage records. Retrieved 22 June 2013
- EXCLUSIVE: Scott Smart (WorldSBK technical director) Interview Part 1 visordown, 31 January 2019. Retrieved 30 October 2021
- Miller, David (27 October 2021). "Paul Smart has died". Bikesport News.
- Sports, Dorna. "Paul Smart passes away". www.motogp.com.