He is the sixth of the nine children of Spiros and Aphrodite Latsis. His father dies in 1929 after a serious accident and John is driven to work from a young age in a variety of jobs at the Katakolo port. He is thus able to support himself and, furthermore, pay his tuition for the Pyrgos College of Commerce, from which he graduates in 1927.

Working hard, with steadfastness and dedication, he starts trading black currants -one of the foremost agricultural products of the Ilia area-, while also building a business as a ship chartering broker and insurance agent at the Katakolo port, and servicing tourists visiting the archeological site of Ancient Olympia from the harbour.

While serving in the Greek Navy for the second time, Latsis gets engaged with and eventually married to Erietta Tsoukala, at the time a student in the all-female Pyrgos High School. Together they will have three children, Spiro, Marianna and Margarita. Soon after their wedding, the couple moves to Athens.

With the help of his friend, shipowner Evangelos Nomikos, John S. Latsis procures his first passenger ship, named “Effi”, and soon after his second one, “Niki”. At the end of this year, he purchases “Laurana”, which he renames “Neraida”. All three vessels work the Saronic Gulf routes; more will join them during the next years. 

The purchase of the cargo vessel “Marianna” signposts his new interest in this particular maritime arena. During the 1950s and 1960s, more freighters join his fleet. In order to better monitor his business affairs, he sets up offices in Cairo, Geneva and London, while his headquarters remain in Athens.

The need to transport molasses in the context of the Egypt-Greece clearing agreement leads to the purchase of his first tanker, named “Spiros”. Already involved in the trade of oil and various products with "Spiros”, as well as with other tankers gradually added to his fleet, Latsis expands his business to transportation, supplying the domestic market, as well as executing transports on a global scale.

Not having succeeded in taking over the transportation line for migrants from Greece to Australia, he provides an ocean liner to the government of Libya for the voyages of pilgrims to Jeddah, Saudi Arabia, on their way to Makkah. This endeavor will continue for several years, with the purchase of additional ships and the extension of the pilgrimage routes from other Muslim countries as well.

Latsis wishes to support young men and women from his birthplace who strive to obtain a higher education. After the Foundation ceases to operate in 2012, the John S. Latsis Public Benefit Foundation takes over in its place, awarding undergraduate and postgraduate scholarships and expanding these activities on a pan-Hellenic scale. To date, approximately 2,000 students have been sponsored through the program.

The first export refinery in the country is created in Elefsina. In 1973, its operations and scope are expanded and it is additionally used to cover part of the country’s domestic needs. Latsis’ own technical team carries out the construction, which includes extensive and complex port and building projects, providing him with a comparative advantage in the construction field.

The Petrola International company launches its operations in the country. Up until the 1990s, Petrola will undertake and complete elaborate port and engineering developments, projects for the royal family, as well as the construction -in a joint venture with Petromin, a state oil company- of one of the world's largest refineries at the time in Rabigh.

A non-profit foundation based in Geneva, it is established to annually award prizes to scientists and research teams in recognition of their outstanding and innovative contributions to various scientific fields.

The acquisition of this small bank located in Geneva is originally made to serve intra-company transactions between the various Latsis Group corporations. In the years to come, John S. Latsis expands his business to the field of private banking and in 1990, with the liberalization of the financial sector, the Euromerchant Bank is established in Greece; it will later develop into Eurobank EFG.

The second largest tanker in the world at the time, with a 550,000 ton capacity, is purchased by Latsis and logged in the Greek Registry. In that same year, he assigns one of his cruise ships to host approximately 1,000 Kalamata earthquake victims; the ship will serve that purpose for a total of 2 years. In 1989, he donates $20 million to the Greek Seamen’ s Pension Fund, an endowment for which he is honored by the Academy of Athens.

The Foundation starts at a time when the needs of the expatriates from the neighboring country are both considerable and urgent. Through specially designed activities, as well as the Vocational Training Centre for Albanian students of Greek descent at Pogoniani, the Foundation will host and train more than 1,000 Greek Albanians, contributing resolutely to the advancement of their lives, as well as to their vocational rehabilitation. The Foundation's operation ceases in 2012.

The same year the Latsio Elementary School building, funded by Latsis himself, is completed and delivered; it covers a total area of 10,000 square meters. A few years later, the construction of the Latsio Burn Center, a specialized unit providing advanced treatment for serious burn and trauma victims, commences. In 2005, the center is delivered fully equipped to the Greek State and housed at the Thriassio General Hospital of Elefsina.

Two years after his passing, his family establishes the John S. Latsis Public Benefit Foundation, to preserve and continue his legacy and commitment to the realisation of projects that serve the public and common good.