New Zealand captain Ross Taylor and batsman Andrew Ellis were hospitalized on Monday after showing signs of stomach flu and dehydration.
The country's cricket board said the two players showed symptoms of stomach flu during the rain-affected, second one-day international at Pallekele International Stadium on Sunday.
Taylor played on but Ellis returned to the team hotel as his symptoms were more severe.
Officials observed signs of dehydration and decided that the two players should stay in hospital for a few hours for rehydration treatment.
Taylor is expected to be fit for the third one-day international on Tuesday, but Ellis' availability will be decided only close to the match.
Taylor was the leading scorer for New Zealand with an aggressive 72 in the second ODI to set up a competitive 250-6. But Sri Lanka won the match by 14 runs on the Duckworth/Lewis method after rain halted the match 22 overs into the hosts' chase.