The WPP-owned network won the business after a competitive pitch against undisclosed agencies.
ZenithOptimedia previously handled the UK media planning and buying for the company but opted not to pitch for the pan-European account, which now includes the £1.3 million UK business.
The company has primarily used TV spots, created by HMDG, to target male consumers. Last year, its "men just want to have fun" campaign was awarded a bronze IPA Effectiveness award.
Kärcher was established in 1935 and remains a family run business. In addition to pressure washers, Kärcher produces dry-ice blasting machines, vacuums, sweepers, scrubber dryers, detergents, vehicle washers and water treatment systems.