Anantharaman (30) was strangled to death yesterday by wife Vidyalakshmi's lover Anand and his friend Anburaj in a deserted spot nearby Kundala dam, they said.
Vidyalakshmi was taken into custody this morning, police said adding that Anand and Anburaj were also arrested.
She was allegedly in love with Anand and conspired with him to kill Anantharaman with whom she got married only on June 7.
The plan was first to kill Anantharaman at Guruvayur, where the couple had gone for worship, but were unable to carry out the plan, police said.
They then reached Munnar on Saturday where Vidya accompanied her husband to the Kundala dam who was strangled to death, police said.
She then raised alarm saying two persons had tried to snatch her gold ornaments and had killed her husband, police said.
However, on being questioned, the woman spilled the beans, police said.