The earliest known inhabitation in the Laajalahti area was in the 13th Century. Farming and using shoreline meadows as pastures were an important part of the area's landscapes up until the middle of the 20th Century. These practises played a part in the area's becoming overly fertile. The main culprits though were the Tali wastewater treatment plant and the rubbish dump at Iso-Huopalahti, which both were taken into use during the 1950s. As a result of these two ventures aquatic plants disappeared nearly completely from the area. After the treatment plant and the dump were closed the area has started to recover; aquatic plants have appeared again and water birds are more abundant in the area.
The nature reserve's location in the heart of the most populated area of Finland has had a profound effect on the area. In the mid-1950s for example the Helsinki University of Technology campus was built in Otaniemi and one third of the Laajalahti area's reedbeds were buried under the building site. Importation traffic routes such as Ring Road 1 (Kehä 1) and Turunväylä have set tight perimeters for the area.
Villa Elfvik (www.visitespoo.fi) at the north end of Laajalahti Nature Reserve was built at the beginning of the 20th Century. At the beginning of the 1990s the town of Espoo renovated the building and it is now a nature centre.