Norwegian culture brought into line with that of other European countries, and he himself followed the romantic tradition, being most closely influenced by J. L. Heiberg. He represented clearness and moderation against the extravagances of Wergeland. He gave an admirable practical exposition of his aesthetic creed in the sonnet cycle Norges Daenaring (1834). He published a volume of Digte in 1839; and in 1845 Nyere Digte. The collections of old Norse poetry made by Asbjdrnsen and Moe influenced his talent, and he first showed his full powers as a poet in Nyere Digte. His descriptive poetry is admirable, but his best work was inspired by his poems on old Norse subjects, in which he gives himself unreservedly to patriotic enthusiasm. Other poems followed in 1848, 1851 and 1859.
His critical work includes Ewald og de norske Digtere (1863), On Ludwig Holberg (1854). Welhaven's Samlede Skrifter were published in 8 vols. at Copenhagen (1867-1869).