A regeneration control system for an oxidation catalyst in an internal combustion engine includes a temperature sensor to produce a temperature signal indicative of an exhaust inlet temperature that is below a regeneration temperature for accumulated hydrocarbons on the oxidation catalyst, an electrically actuated boost leakage valve, and a regeneration control unit. The regeneration control unit commands an adjustment to the position of the electrically actuated boost leakage valve to increase leaked boost to increase exhaust temperature to the regeneration temperature by way of increased air-fuel ratio. Related methodology is disclosed.