CI is the world's largest coal miner and accounts for about 80% of India's output.
The company frequently falls short of its output targets due to employee strikes and delays in getting approvals to expand mines, among other issues.
The ongoing dispute is reported to be over pay-related issues.
"Coal Mines Officers' Association of India has served a strike notice ... against non-finalisation of performance related pay, new pension scheme and other demands," the company said in a statement to the Bombay Stock Exchange on Wednesday.
Chairman S Narsing Rao told Reuters the company expected to produce about 475 million tonnes in the financial year ending March 31 and raise its production by 30% next year.
India's coal imports rose 21% to 152 million tonnes in 2013 calendar year, according to research firm OreTeam.
Coal India shares have fallen more than 10% so far this year, worsening last year's losses of 18%.
