Sheffield Supertram has seen a drop in passenger revenue for the seventh year running, figures from the Department for Transport (DfT) show.The network's income fell from £12.6m in 2014/15 to £11.4m last year and by almost 30% since 2008/09, when it generated £16.2m.
Passengers numbers, however, have risen from 11.5m to 11.6m in the last year.
A spokeswoman for Stagecoach, which runs Supertram, said the network remained a "profitable business".
The DfT report shows Supertram and London Tramlink are the only services out of England's eight light rail and tram networks to have seen a drop in revenue in the past 12 months.
It said the figures for Sheffield had been affected by a £32m rail replacement project, which began in 2013.
Stagecoach said: "When we began operating Supertram services in 1997, the network was a drain on the public purse - we have turned the service into a profitable business which no longer relies on public funds and is depended upon by millions of people every year.
"Alongside South Yorkshire Passenger Transport Executive, we have just completed a vital three-year programme of investment work to help maintain the network for decades to come.
"Since this work finished there has been a significant increase in the number of passenger journeys.
"Sheffield benefits from a good public transport network and customers have a choice of integrated tram, bus and rail services, so it is clear that people will use different modes of transport at different times depending on their specific requirements."
A recent survey found 97% of passengers were satisfied with the tram service in Sheffield, compared to 81% for the Midland Metro network and 98% for the Nottingham Express Tramway.