Astrup was a distinctive, innovative artist noted principally for his intense use of color depicting the lush landscapes of Vestlandet featuring the traditional way of life in the region.

He was the eldest son of eleven children born to Christian Astrup (1844–1919) who was a parish priest at Ålhus Church in Jølster.

In 1913, Astrup settled with his wife and children in Sandalstrand (now Astruptunet) on the south side of Lake Jølstravatn across from the village of Ålhus.

Astrup preferred clear, strong colors and usually made landscape art depicting his surroundings in Jølster.

Having spent the majority of his life in Jølster, the landscape proved a strong influence and through his paintings he sought 'a national "visual language" that evoked the traditions and folklore of his homeland'.

[8] His paintings describe an intimate interaction between nature and the developed environment, characterized by bold lines and distinctive rich color.