The company said it was confident that full-year revenue growth would be in line with a medium-term aim of between 4 and 6 percent and saw further expansion in 2018.
For the past four years, G4S, which provides services such as guarding, aviation screening and mobile patrols, has been selling businesses to pay off debt and trying to limit losses from British government contracts, gradually getting a greater share of its revenue from abroad.
Revenue for the six months to end-June rose 6 percent to 3.7 billion pounds ($4.8 billion) and earnings after tax reached 128 million.
"During the second half of 2017, our growth programme will focus on consolidating contract wins made over the past year and on converting attractive opportunities in our pipeline," Chief Executive Ashley Almanza said.
Net debt to earnings before interest, taxes, depreciation and amortisation stood at 2.7 times, setting it up to reach its target of 2.5 times or lower by the year end.
An employer of 600,000 staff, G4S also installs and monitors alarms, closed-circuit television, gateway control and biometric systems.
Its shares have risen 40 percent in the year to date as its overhaul starts to bear fruit.
(Reporting by Elisabeth O'Leary; Editing by Paul Sandle and David Holmes)