Almost all aspects of geotechnical engineering are present in harbour works, namely foundation engineering, stability problems, above and under water, dredging, and the knowledge of sediments features, both geotechnical, key to define the type of dredger to use, and gradation and composition, since the chemical and organic contamination of those sediments define the final destination of the dredged material. But cliffs are also important, as often they overtop the harbour facilities and/or their accesses. One must also emphasized the presence of soft soils, the necessity of their improvement, related to structure and engineered fill foundations. Underwater embankments and their particular construction processes and quality control are also central. This paper presents the main geotechnical aspects of the Portuguese small harbours, detailing three major concerns: dredging, cliff stability and foundation of structures and embankments on soft soils.