Smargiassi was born in Vasto, Chieti. Initially aiming to be a priest like his uncle, an artistic talent was recognized, and he was sent at age 19 to train in Naples. briefly with Giuseppe Cammarano, and then for seven years with Anton Sminck van Pitloo. He then traveled to Rome, where he was briefly tutor to Louis-Philippe, future king of France. He was patronized in Paris by the Salon of the Duchess of Saint-Leu. When Pitloo died in 1837, Smargiassi returned to Naples to fill the chair of Professor of Landscape painting for the Academy of Arts in Naples. The other candidate for the position was Salvatore Fergola. In Naples, he was patronized by the Count of Aquila. Giacinto Gigante was a contemporary and fellow-painter, while Francesco Mancini, Alfonso Simonetti, and Raimondo Scoppa were among his pupils.
He specialized in paintings including rural landscapes. He died in Naples.
- (in Italian) Smargiassi, Gabriele.| Enciclopedia Italiana., Treccani
- Napier, Lord Francis (1855). Notes on Modern Painting at Naples.. West Strand, London: John W. Parker and Son. pp. 70–75.