Food poising is suspected behind the mass illness of the people who attended the feast in the Kahu village of Nuwakot on Tuesday, police said.
All those who fell ill have been admitted to the local hospital and the condition of 22 is serious.
The villagers who attended the birthday party had complained of vomiting, diarrhoea, and muscle pain.
Some of the local people have also attributed unhygienic drinking water for the illness as the people of the area use the common stream for drinking water since safe source of drinking water in the villages dried up after last year's devastating earthquake.