Compass said its offshore and remote business faced pressure from low commodity prices as oil companies cut jobs and shut sites.
Organic revenue in the division fell 22% due to business closures and lower volumes, although it still won new deals including an extra site for Canada Natural Resources Limited.
Overall underlying operating profits in the six months to the end of March rose 4.8% to £724million on a 5.8% increase in revenue to £9.7bn.
Compass, which has restructured divisions such as offshore and remote to take account of the weaker trading, increased its interim dividend 8.2% to 10.6p.
Chief executive Richard Cousins said: "Savings from the restructuring are starting to come through, and are offsetting the weakness in offshore & remote and some emerging markets.
"In the longer term, we remain excited about the significant structural growth opportunities globally and the potential for further revenue growth, margin improvement, as well as continued returns to shareholders through dividends and ongoing share buybacks."