CAS overturned the IIHF's decision to exclude Russia from competitions during the 2026-27 season, including the men's and women's world championships.
In a brief statement, CAS said the IIHF's security concerns were not supported by sufficient evidence.
The court stressed that its ruling did not address whether Russia should be required to compete without national symbols as a team of neutral athletes, as in some other Olympic sports, or any other "organisational consequences".
The IIHF expressed disappointment with the decision, maintaining that its previous rulings had been necessary to protect the safety and security of participants and safeguard the integrity of its competitions.
"While the IIHF respects the authority of CAS and will act in accordance with its ruling, the outcome does not remove the concerns that informed its assessments," the governing body said.
Russian sports minister Mikhail Degtyaryov wrote on Telegram that CAS had "recognised the demands of the Russian Hockey Federation on key points as justified".
The IIHF has excluded Russian teams from its world championships since Russia invaded Ukraine in 2022. Russia also missed this year's Olympic ice hockey tournaments.
The ruling presents an immediate challenge for the new IIHF president, Franz Reindl, whose home country, Germany, is due to host next year's men's world championship.