The Sound of Islay scheme, developed by ScottishPower Renewables, will receive almost £16.8m to progress plans for 10 underwater turbines in a sheltered channel between the isles of Islay and Jura.
Meanwhile, the Kyle Rhea project will get almost £15m to build SeaGen turbines developed by Siemens subsidiary Marine Current Turbines.
The devices will be installed between the east coast of Skye and the Scottish mainland.
Lindsay Leask, senior policy manager for Scottish Renewables, said: "This is great news for the tidal industry in Scotland.
"It's this kind of financial commitment that helps harness further private investment."