The Sree Krishnaswamy temple at Ambalapuzha dedicated to Parthasarathy was established by the Chembakasserry Pooradam Thirunal-Devanarayanan Thampuran in the year 790 M.E. He offered his state to Sree Krishna and ruled the country as his regent after assuming the name of Deva Narayana
Ambalapuzha, the Land of Lord Krishna is the most gifted tourist and pilgrim center in Kerala. The main attraction is Ambalapuzha Sree Krishna swami temple. In olden days Ambalapuzha was known as Chempakassery. Chempakassery is formed from a ship named Chempaka. The kingdom derived its name from a kind of locally called 'Chempaka' which frequently the waters of the Alleppey coast. The kingdom came to be known as Ambalapuzha only after the construction of the present Sree Krishna Swami Temple at Ambalapuzha in the 16th century by Pooradam Thirunal Thampuran. Once Pooradam Thirunal Thampuran, travelling in a boat with Vilwamangalam Swamiyar. Then suddenly heard the melodious strains of the flute. The music came from the peepal tree stands. The sage, can understand that the music was that of the Lord Krishna.
Vilwamangalam Swamiyar thus helped the Thampuran to have a vision of Sri Krishna in the same way as he had helped Manaveda Zamorin to see God. Inspired by this the Zamorin wrote the Krishna Gita. Now the Thampuran was inspired to build a temple and install a Gopala or cowherd Krishna at the spot. Accordingly a beautiful temple was built and an idol of Sri Krishna in black granite stone was carved out for installation. Kudamaloor kadiyokkal namboothiri is going to install the Vigraha. Then Puthumana Valia Namboothri refuse to install that vigraha. Every one disappointed at this. Someone even challenged the Thantri to prove his point. It did not take long for the Tantri to do so, well-versed as he was in mantras, tantras and Sastras. All he did was to tap with a piece of iron, at the damaged spot and out jumped a frog and some dirt liquid!.
The Thampuran felt most unhappy at the turn of events. It was again Vilwamangalam Swamy who came to rescue and advised him to get the idol of Parthasarathy from Kurichi, a neighboring place belonging to Thekkumkoor Raja. But it was not an easy job because the Thekkumkoor Raja was not on friendly terms with the Champakasseri Thampuran. If the idol was taken by force, a fierce contest might follow between the two ruler and who could forecast that the Champakasseri Thampuran would come out successful in the contest. And if the idol was stolen that would be unbecoming of a ruler and in any case it would be unfit for consecration being tainted by the sin of stealth.
The Thampuran's minister went to Kurichi and quietly got permission from the owner of the idol.The same night the minister, accompanied by a handful of soldiers, reached the border of Thekkumkoor by country boats. He got the idol of Krishna. Next morning the minister and party arrived at Champakulam madam where the Thampuran went to receive the idol, which was ceremoniously taken to the temple. This event took place on the Moolam day of a Mithunam.
It is to keep the memory of this that the Champakulam Moolam Boat Race (June-July). The idol was duly installed in the temple at a propitious time on Thiruvonam day in Mithunam in 1613 A.D. Ambalapuzha idol is Lord Parthasarathy.