According to party sources, Tharoor, who is aiming for a hat-trick from Thiruvananthapuram Lok Sabha constituency, sustained injuries on his head, which required six stitches.
The 63-year old MP also suffered a minor leg injury in the incident which occurred at a Devi temple here.
'Thulabharam' is a Hindu ritual in which a person is weighed against a commodity such as flowers, grains, fruits and similar articles in temples and the equal value or quantity is offered as donation.
Monday being the Malayalam new year day ('Vishu'), Tharoor performed the ritual by offering sugar equal to his weight in the morning before embarking on his poll campaign.
He was accompanied by his family members and party leaders and workers including MLA, V S Sivakumar.
While he was sitting on one of the pans of the weighing scale, the hook came off and fell on his head, the party sources added.
He was taken to Trivandrum Medical College hospital for detailed examination, the sources said.