Firms are being urged not to score an "own goal" by refusing to be flexible with requests from staff to watch games during the football World Cup in the coming weeks.
The TUC said managers should allow people to work from home, start early or late or even provide a TV on company premises to show matches.
Flexible working has real benefits for bosses and workers, said the TUC.
General secretary Frances O'Grady - an England and Arsenal supporter - said: "Millions of workers around the UK will want to cheer on their national teams.
"Tournaments like this can be great for building camaraderie at work, with colleagues running sweepstakes and spending time together.
"It's important employers do not score an own goal by acting like killjoys.
"To avoid problems they should try and let people who want to watch the games do so, either at work or at home, and then claim back their time afterwards.
"Whether it's major sporting events like the World Cup or watching your kids take part in their school sports day, allowing people more flexibility in how and when they do their work makes them happier and more productive."
Rosena Allin-Khan, Shadow Sports Minister, said: "Labour echoes the call the TUC has made, asking employers to be flexible with staff wanting to watch the World Cup.
"As a nation, we're proud to cheer on England in the World Cup and we believe that employers should be flexible with fans supporting our national team in the coming weeks."