The Treaty of Tordesillas had a significant impact on the economic policies of Spain and Portugal in the 16th century. For Spain, the acquisition of vast territories in the Americas led to the establishment of a colonial economic system that focused on extracting resources, such as silver and gold. This influx of wealth enabled Spain to become a major economic power in Europe. Portugal's focus shifted to establishing and maintaining trade routes, especially in spices, which were highly valuable in Europe. Both countries developed mercantilist policies, seeking to maximise exports and accumulate wealth, which was a common economic practice during this era.

Other European powers, particularly England, France, and the Netherlands, were not part of the Treaty of Tordesillas and initially did not recognise its legitimacy. They viewed the treaty as a bilateral agreement that unfairly monopolised new lands for Spain and Portugal. This led to tensions and rivalries, as these countries began to challenge the Spanish and Portuguese dominance in the New World. Their objections were rooted in the desire to participate in the lucrative opportunities presented by the new territories. This eventually led to increased exploration and colonisation efforts by these nations, directly challenging the Spanish and Portuguese claims.

The Treaty of Tordesillas significantly influenced navigation and mapping practices during the Age of Exploration. The need to accurately determine the demarcation line led to advancements in cartography and navigation. Mariners and explorers were compelled to develop more precise methods for calculating longitude and latitude, which were crucial for adhering to the treaty's terms. This period saw an improvement in the quality of maps, with greater emphasis on accuracy and detail. The treaty effectively stimulated the scientific aspect of exploration, as accurate navigation became crucial for both Spain and Portugal to enforce their territorial claims.

After the signing of the Treaty of Tordesillas, Spain and Portugal took immediate actions to solidify their claims. Spain expedited its explorations and conquests in the Americas, sending expeditions to map and claim territories. This led to the discovery of new lands and the establishment of colonies. Portugal, on the other hand, focused on establishing its maritime routes to Africa and Asia, particularly India and Brazil. They set up trading posts along these routes, securing their control over the spice trade and other valuable resources. These actions were instrumental in establishing the two countries as dominant colonial powers.

The Treaty of Tordesillas played a foundational role in the development of international law, particularly in the concepts of sovereignty and territorial rights. Although not immediately recognised as a legal precedent by other nations, the treaty introduced the idea of dividing the world into spheres of influence, which was a novel concept in international relations. It set a precedent for future treaties and agreements regarding territorial claims and the rights of nations to undiscovered lands. The principles established in the Treaty of Tordesillas can be seen as early steps towards the modern understanding of international law governing territorial disputes and the rights of nations.