The oldest traces of settlement within the Municipality of Ożarów Mazowiecki are concentrated around the area of the Mrowa river (currently the Utrata river) and the villages of Umiastów-Kręczki-Płochocin.

1342 – first references of Ożarów during the reign of the king Casimir the Great.
1475 – Ożarów was the settlement of the Duke of Mazovia.
1526 – Ożarów became a royal village.
1565 – according to the inspection record, the village and the manor farm of Ożarów known earlier as Pożarów was the property of the Polish King, but was under the rule of the Starost of Warsaw, Krzysztof Sobek.
1620 – Ożarów became the property of the Province Governor Mrs Warszycka. After her death it was owned by Antoni Brzozowski and after 1773 as the non-city Starosty, it was forwarded to Wojciech Szamocki the warrant officer of Warsaw, together with other manor farms in the outskirts of Warsaw.
1795 – Ożarów was in the Prussian Partition where the Germanisation of the region took place.
1807 – pursuant to the Treaty of Tylżyca, the Duchy of Warsaw was established as an independent state in alliance with France. The Duchy was formed with the 2nd and 3rd Prussian Partition areas, including Ożarów. In 1813 the Duchy of Warsaw was taken over by the Russian army and two years later it ceased to exist. After the Vienna Congress, the five sixths of the Duchy of Warsaw was transformed into the Kingdom of Poland, the monarchy with the Tsar of Russia as the king. The lands of Ożarów were now within the Kingdom of Poland.
1827 – the village contained 32 houses and 257 inhabitants.
1864 – some parts of the farm manor lands were in the possession of peasants under the Tsar’s ukase, provided that the lands were redeemed by the villagers.
1876 – the manor farm of Ożarów was 1100 morgen (a unit of measurement) big and the village itself was 138 morgen. In the 19th century in the Russian Partition the changes to the administrative and territorial divisions in the municipality took place.
1901 – the Glassworks of Ożarów was created. It was located at the village estate called Franciszków. It was the beginning of the industrial development of Ożarów Mazowiecki.
1911 – a join-stock company ‘Town-Garden’ was established and the engineer Mr Majewski created 142 parcels on 60 morgen, where the Mickiewicz estate was built. Wide streets were planted with fruit trees. The revenue from the sale of the fruit was used for the improvement of the land.

1929 – the Cable Factory in Ożarów was established, in 1930 the first primary school was built. A strong agricultural economy was dominating within the manor farm village estates.

As a result of the subdivision, a number of estates was created along the historical western route. Mickiewicz, Franciszków, Zientarówka and Balcerówka estates were created. The second phase of the economic development is connected with the launch of the so-called Kaliska Railway which joined Ożarów with Warsaw.

1918 – most of the Mazovia lands were included into the Warsaw Voivodship. Until 1948 the area of the current Municipality of Ożarów Mazowiecki belonged to the District of Błońsko and Warsaw, and then after the eradication of the Błońsko District it was included in the Grodzisko District.

The outbreak of the Second World War got people involved in the fight against the occupying power. Many residents demonstrated their bravery and patriotism. We can find numerous monuments and places of remembrance recalling the heroic deaths of the Polish soldiers and insurgents in the area. They include cemeteries, shrines, commemorative plaques, crosses and boulders.

1939 – 996 soldiers died on the fields of Ożarów where the Łódź and Modlin Army fought. Two temporary shelters for the members of the Warsaw Uprising were organised. The Pallotine priests and Ursuline Sisters taught people in secret.
1944 – the ceasefire agreement was signed at the manor in Poniatowskiego Street in Ożarów.
1st July 1952 – the area of the Municipality of Ożarów was included into the Pruszków District.
1957 – Ożarów-Franciszków was granted the estate rights.
1967 – Ożarów was granted the town rights and was named Ożarów Mazowiecki.
1989 – the town emblem was established.
2003 – the town and municipality banner was established.
2017 – the celebrations of the 50th anniversary of Ożarów Mazowiecki being granted the town rights.

In the 1990s the area of Ożarów Mazowiecki was included into the newly established West-Warsaw Distrrict.