The first buses delivered in 1920 were twenty 31-seat Straker-Squire vehicles with solid tyres.

By 1927 the fleet included Burford, Shelvoke and Drewry, Guy and AEC models and totalled 57 buses; The tram replacement scheme of 1930 saw the introduction of double-deck buses, initially Leyland TD1s.
by 1929 it had expanded to 83.
As well as more Leylands, some Dennis Lancet buses were brought for later route conversions.
In 1935 the city's first diesel-engined double-deck buses were delivered (more Leylands); some as tram replacements and others so that older single-deck buses could be replaced.
During the war a mixture of buses were acquired as few new buses were being built.
Further Leyland Titan PD1 buses were delivered once production resumed after the war, but the spread of suburbs onto the hilly hinterland saw more powerful Leyland PD2s entering service from 1948.

Leyland Atlanteans were introduced from 1960.
These had rear-engines and front entrances which eventually paved the way to conversion to one man operation from 1968.
Single-deck buses reappeared in the fleet in 1975 in the shape of Leyland Nationals.
In October 1986 85 Renault/Dodge S56A minibuses was introduced, which represented 70% of the Citybus fleet at the time.
These allowed narrow housing estate roads to be served and service frequencies to be increased on existing routes.
They were replaced by Mercedes-Benz 709D minibuses.
Mid-size single deck buses replaced most double-deck vehicles on busier routes to give high service frequencies, principally Dennis Darts.
The first buses delivered in 1920 were twenty 31-seat Straker-Squire vehicles with solid tyres.
By 1927 the fleet included Burford, Shelvoke and Drewry, Guy and AEC models and totalled 57 buses; The tram replacement scheme of 1930 saw the introduction of double-deck buses, initially Leyland TD1s. by 1929 it had expanded to 83. As well as more Leylands, some Dennis Lancet buses were brought for later route conversions. In 1935 the city's first diesel-engined double-deck buses were delivered (more Leylands); some as tram replacements and others so that older single-deck buses could be replaced. During the war a mixture of buses were acquired as few new buses were being built. Further Leyland Titan PD1 buses were delivered once production resumed after the war, but the spread of suburbs onto the hilly hinterland saw more powerful Leyland PD2s entering service from 1948.
Leyland Atlanteans were introduced from 1960. These had rear-engines and front entrances which eventually paved the way to conversion to one man operation from 1968. Single-deck buses reappeared in the fleet in 1975 in the shape of Leyland Nationals. In October 1986 85 Renault/Dodge S56A minibuses was introduced, which represented 70% of the Citybus fleet at the time. These allowed narrow housing estate roads to be served and service frequencies to be increased on existing routes. They were replaced by Mercedes-Benz 709D minibuses. Mid-size single deck buses replaced most double-deck vehicles on busier routes to give high service frequencies, principally Dennis Darts.
Plymouth Citybus