He was born in Postojna in western Slovenia (then part of Yugoslavia), and spent his youth in the town of Nova Gorica on the border with Italy.

His songs are frequently witty and unusual reflections on eternal subjects such as love, passing and death, and also about the joys of life, particularly wine and good food.

Survival tactics, idiosyncrasies and anxieties of simple people are some of the constant themes of Mlakar's songs, as are joy for life and the seeking of pleasure.

He sings about the simple Slovene man and woman of the 20th and 21st centuries, who are frequently oppressed by big historical events such as the world wars, expansionist policies of large nations, changing political regimes, unstable economic situations and shifts in moral and social customs.

The characters of Mlakar's songs cope with these circumstances in different ways: they either stubbornly defy them ("Karlo Špacapan"), frequently becoming silly and pathetic in the process ("Pepi Žbaradorija"), accept them with a sense of poetic fatalism ("Bertolin in Štefana"), or opportunistically try to accommodate to them ("Politik Gvido").

Many of his songs narrate outbursts of anger directed against authority: some of them result in a temporary victory ("Ivo Balila"), some end in compromise ("Pubi usidma se"), while others remain a dream of a distant future egalitarian retaliation ("Puntarska", "Politik Gvido").

Many lyrics are an intelligent ironic comment on acute problems of contemporary Slovenian society, such as alcoholism ("Beštija"), drug abuse ("Marjo Špinel") and suicide ("Briškula").