Linkage College on Weelsby Road, Grimsby, said facilities for 20 students with physical disabilities would be added at a cost of £430,000.
The college already caters for 100 students with learning difficulties, aged between 16 and 25.
College principal Matthew Orford said the work was a “crucial step” for disabled students in the area.
Linkage Community Trust, which runs the college, said the new building would have physiotherapy facilities, accessible changing rooms and tutorial areas.
The trust has provided education, care and employment for 16 to 25 year olds in Lincolnshire since 1976.
The site at Weelsby Road has been a college since 1982.
The charity also runs campuses in Louth and Spilsby in Lincolnshire.
A trust spokesperson said the new building, supported by the Education Funding Agency, would hopefully open in March.