Harwell contains two 13th-century houses, each of which is a Grade II* listed building.
Lime Tree Cottage in High Street was built about 1250 and remodelled about 1300.
A cross-wing was added about 1360 and the house was given a new front about 1700.
Gable Cottage and Tibbleton Cottage in Wellshead Lane were originally one timber-framed house, built in about 1295 and extended with a new front range in the 17th century.

Bayllols Manor house at Middle Farm is a timber-framed 14th-century hall house, and its service wing may be the remains of a 13th-century building.
In 1589 an upper floor was inserted in the 14th-century hall and some pargeting was applied.
The farm has two 14th-century barns, each of which is Grade II* listed.
One is the Cherry Barn, which was built about 1350 and has 15th- and 17th-century outbuildings.
The other was built around 1365 and has a cruck frame.

Geering Almshouses are a row of brick-built almshouses built by a charity established in 1715 but the houses themselves may not have been built until about 1723.
The almshouses are a Grade II* listed building.

The White Hart in High Street is an early 17th-century timber framed building with early 18th- and mid-19th century brick-built extensions.
It now trades as the Hart of Harwell pub and restaurant.

Harwell once had five pubs and a brewery.
The former brewery is a 17th-century building in the High Street with an 18th-century malt house and 19th-century extension.
It is now a private house.

The Crown in High Street was converted into a nursing home, which was run by Southern Cross Healthcare and ceased trading in 2012.
The Chequers, The Crispin and The Kicking Donkey have all been converted to private houses.

On 4 April 1899 Berkshire Constabulary PC John Charlton was killed in an affray outside the Chequers.
His two killers were felled and arrested by another officer, PC Thomas Hewett and later sentenced to 20 years hard labour for manslaughter.

The Great Western Main Line was built through the north of the parish and opened in 1840.
Originally the nearest station was Steventon, about 2 miles (3 km) northwest of Harwell, which the Great Western opened in 1840.
In 1844 the GWR opened Didcot railway station about 2 ¹⁄₂ miles (4 km) northeast of Harwell.
In 1964 British Railways closed Steventon station, making Didcot (now Didcot Parkway) Harwell's nearest rail link.

Until the Second World War Harwell may have been best known for its cherry orchards.
Harwell contains two 13th-century houses, each of which is a Grade II* listed building. Lime Tree Cottage in High Street was built about 1250 and remodelled about 1300. A cross-wing was added about 1360 and the house was given a new front about 1700. Gable Cottage and Tibbleton Cottage in Wellshead Lane were originally one timber-framed house, built in about 1295 and extended with a new front range in the 17th century.
Bayllols Manor house at Middle Farm is a timber-framed 14th-century hall house, and its service wing may be the remains of a 13th-century building. In 1589 an upper floor was inserted in the 14th-century hall and some pargeting was applied. The farm has two 14th-century barns, each of which is Grade II* listed. One is the Cherry Barn, which was built about 1350 and has 15th- and 17th-century outbuildings. The other was built around 1365 and has a cruck frame.
Geering Almshouses are a row of brick-built almshouses built by a charity established in 1715 but the houses themselves may not have been built until about 1723. The almshouses are a Grade II* listed building.
The White Hart in High Street is an early 17th-century timber framed building with early 18th- and mid-19th century brick-built extensions. It now trades as the Hart of Harwell pub and restaurant.
Harwell once had five pubs and a brewery. The former brewery is a 17th-century building in the High Street with an 18th-century malt house and 19th-century extension. It is now a private house.
The Crown in High Street was converted into a nursing home, which was run by Southern Cross Healthcare and ceased trading in 2012. The Chequers, The Crispin and The Kicking Donkey have all been converted to private houses.
On 4 April 1899 Berkshire Constabulary PC John Charlton was killed in an affray outside the Chequers. His two killers were felled and arrested by another officer, PC Thomas Hewett and later sentenced to 20 years hard labour for manslaughter.
The Great Western Main Line was built through the north of the parish and opened in 1840. Originally the nearest station was Steventon, about 2 miles (3 km) northwest of Harwell, which the Great Western opened in 1840. In 1844 the GWR opened Didcot railway station about 2 ¹⁄₂ miles (4 km) northeast of Harwell. In 1964 British Railways closed Steventon station, making Didcot (now Didcot Parkway) Harwell's nearest rail link.
Until the Second World War Harwell may have been best known for its cherry orchards.
Harwell, Oxfordshire