Emergency services were called to River View Maltings, Grantham, at about 11:30 GMT, on Thursday.
The 42-year-old man was airlifted to the Queen's Medical Centre, Nottingham. Details of his condition are yet to be released.
The scene has been cordoned off while officers carry out a forensic investigation.
A 41-year-old woman has been arrested after a man was stabbed at a house in a Lincolnshire market town.