The attack last night came ahead of the launch of 'Jan Raksha Yatra' today by the saffron party.
The attack took place around 9:30 pm when BJP workers were decorating a part of the National Highway-66 for the 15 -day march, which will be launched by BJP chief Amit Shah.
The three injured BJP workers were being treated at a private hospital in Neeleswaram, the police said.
No case has been registered in connection with the incident so far.
BJP Kasargod district secretary Sreekanth alleged that nearly 20 CPI(M) workers attacked BJP activists without provocation, while they were decorating a road side at Neeleswaram market.
CPI(M) cadres, who cannot tolerate the "growing political influence" of the BJP in the state were indulging in such attacks, he alleged.
Around 15,000 BJP cadre were likely to participate in the march, Sreekanth said.