This paper provides a detailed analysis, for the first time, of the stucco decorations in the representative salons on the second floor of the Sugar Refinery Palace in Rijeka. Despite being an extremely important group of secular stuccos, it has, until now, lacked a thorough iconographic and stylistic analysis and contextualization. Furthermore, no models or masters who produced them have been identified. The Sugar Refinery Palace, specifically its administration building, served as the headquarters of the Privileged Trieste-Rijeka Company, founded in Trieste in 1750 to establish sugar trade in the Habsburg lands. Administration and production were relocated to Rijeka in 1752, when the central industrial complex was organized, and the Administration building was erected. Following the devastating fire of 1785, the building underwent reconstruction, and it was raised in height while acquiring a new representative staircase. It was assumed that the architect behind the renovation was Andrea Menini from Treviso, and recently discovered archival data confirm his presence in Rijeka during 1786. The stone decoration, part of the restoration, also reveals the contribution of Sebastiano Petruzzi, the most prominent sculptor and builder in Rijeka at the time, and his workshop. Between 1786 and 1789, the period to which the frescoes in the western salon with architectural capriccios have been dated, the decoration of the central Ceremonial Hall and the two flanking salons on the western and eastern sides along the façade was executed. The central hall features Corinthian pilasters with beams and is covered by a cloister vault decorated with war trophies and four figural medallions. Although the exact iconography of these compositions has not been determined, it is assumed that they depict scenes from the lives of Roman emperors, possibly the reigns of two “bad” emperors - Domitian and Vitellius - who met violent death, and their “good” counterparts Vespasian and Titus. The overall decoration of this hall reflects late Baroque or Josephine Classicism characteristic of the enlightened Joseph II Habsburg’s reign (1780-1790), manifesting renewed enthusiasm for the art of ancient Rome, its rationality, simple austerity, and cold sublimity. Therefore, the decoration of this hall incorporates numerous models derived from ancient and Renaissance traditions, reshaped in the manner typical of the second half of the 18th century. Notably, the early neo-Classical style in Italy and in Habsburg Tuscany during the time of Joseph’s brother, Grand Duke Peter Leopold II, played a crucial role, with his Florentine residence in Poggio Imperiale, decorated by two stucco masters, brothers Giocondo and Grato Albertolli. In the lateral salons, the finely detailed decoration is still executed in the spirit of late Rococo and painted in soft pastel tones. The cornice under the vault features stucco cameos depicting famous ancient statues, such as Venus Callipyge or Cupid and Psyche, while the ceiling is adorned with war trophies collaged from various graphic templates of the time. Based on stylistic and formal analysis, the stuccos from Rijeka can be associated with the brothers Clemente (Montagnola, 1758 - Kaštel Lukšić, after 1810) and Giacomo (Montagnola, 1763-1838) Somazzi from the Swiss Canton of Ticino. They left a significant stucco oeuvre in numerous churches across Kvarner, the Croatian Littoral, and northern Dalmatia during the late 18th and early 19th centuries. The stuccos from Rijeka would be their earliest and only preserved secular work. It is plausible that the brothers worked as part of a larger workshop in Rijeka before starting their career as independent masters in the last decade of the 18th century. It may have been the workshop of Sebastiano Petruzzi, where Clemente is mentioned as an associate and partner in Rab during 1790.