Labour disputes resulting in strikes can hamper port and terminal operations and even result in de facto port or terminal blockages. Labour unions are typically very visible in port contexts, although major differences in union power can be observed across seaports and countries. Labor unions (representing dockworkers and pilots) initiate most port strikes, often disagreeing with: (i) planned port reform schemes; (ii) nautical service provision reforms; (iii) wage levels and remuneration; and (iv) overall working conditions and arrangements forming part of collective bargaining agreement negotiations.

The 2002 port strikes involving 29 ports on the American West Coast, were highly disruptive events for transpacific trade and a key contributing factor for the further expansion of all-water routes to the East Coast through the Panama Canal by maritime shipping lines. This shift was an important factor in the decision to expand the Panama Canal, which was finally achieved in 2016.

Terminal automation can also be a source of labour unrest. For example, the new APM terminal development at Maasvlakte 2 in Rotterdam faced strong opposition from local labour unions as they feared the possible loss of jobs and lower wages as the work conducted by quay crane drivers was transferred to remote operators of automated quay cranes.

When a strike lasts several days or even weeks, the disruptions can spread to neighbouring ports as many ships head to other terminals. Ports affected by regular and extended strikes can incur major reputational damage and a loss of trust among market players. The impacts can be far-reaching and can lead to, for example, structural shifts of cargo volumes to rival ports, as well as sharp decline in port investments by international companies. The risk of strikes can be reduced by structures allowing a social dialogue between workers and management, and effective management of stakeholder relations. Social dialogue through effective joint consultation bodies is considered key to a sustainable relationship between employers and labour unions. When industrial relations are good, labour unions can contribute to enhancing the service provision process and labour productivity. Unions can help dock workers and nautical staff participate effectively in improving performance by critiquing existing work methods, resulting in a safer working environment. A climate of constructive dialogue enhances social peace in ports.