The 1877 Act constituted the trust port to manage, maintain and regulate the Port of Lerwick.  Promotion of the Act was funded by the merchants of the town and a board of trustees was established. The first task was to build a pier and Victoria Pier opened in 1886.

As a Trust Port, the harbour is operated commercially by the Port Authority which, although not publicly funded, is accountable to the wider Shetland community, as well as harbour users. As a self-financing business, it depends like any commercial concern on cash flows and profits for its successful operation.

The Trust Port status also means all profits are reinvested in the maintenance and development of the harbour to ensure the varied requirements of customers continue to be met. Over £80 million has been invested in port assets over the years.

Mindful of the wider community, the Authority also provides stakeholder benefits through leisure and amenity improvements and involvement in community events.  

To keep pace with changing requirements of port users and the Shetland community means a close working relationship with them to identify opportunities for development and diversification.

Included in the Authority's key objectives are continuous improvement of its environmental performance, investment in new port facilities; diversifying sources of income, especially where supporting core activity; attracting new business and continuing to satisfy customers; maximising quality and value-for-money for all services; and operating safely.

The name changed from Lerwick Harbour Trust to Lerwick Port Authority in 1999.