Evidence of the earliest human settlements are found at the sites of Kobeaga I and II (Barainka), Urtiaga cave (unexcavated) and of Jentilkoba of Iperratx (Solarte) and of Otoioko Jentilkoba (Artika), with the first two being the most notable. Kobeaga II constitutes the first indication of human settlement in Ispaster, as it is a settlement of Mesolithic fisher-folk; it is datable to around 3,500 B.C., just prior to the onset of the Neolithic period.
At Kobeaga I numerous bone objects of adornment and ceramic remains have been found including fragments of beakers. The chronology is difficult as it is probably a Bronze Age burial site.

Middle Ages

Ispaster The first recorded mention in history made of Ispaster does not occur until a decree by King Alfonso XI in 1334 for the tithes paid by hunters of Amoroto, Ispaster, Gardata and Asumendi to be restituted to the church in Lekeitio. Ispaster, organised into an elizate, a local administrative body of the time, was in frequent in conflict with the neighbouring town of Lekeitio, which fits in the backdrop of the wider conflict between towns and the Flat Lands affecting the whole of Bizkaia.
However, the great conflict that caused so much strife in the lives of people throughout Bizkaia during this period was none other than the local Wars of the Bands between the Gamboino and the Oñaz factions that swept the Basque region during the 14th and 15th centuries. Lasting two centuries, the conflict was long and extremely harsh with Ispaster siding with the Oñaz band, whose local leader belonged to the Adan de Yarza lineage, Lords of Zubieta.
The end of this convulsive period was marked by the offensive against the two factions initiated by King Henry IV in the year 1457 and concluded by the Catholic Monarchs in 1492.

Early Modern and Contemporary periods

A study of the demographics of the Early Modern and Contemporary periods shows periods of population waxing and waning due mainly to bad harvests, epidemics and war. As a result, population growth would not stablise until the 20th century.
The inhabitants of the elizate, a local administrative body of the Middle Ages, of Ispaster were principally farmers, raising livestock, or to a lesser degree fishermen with ties to the village Lekeitio. The introduction of maize in Ispaster in 1614 would have far reaching consequences, just as throughout the rest of the region.
Parallel to the growing of maize is the rise in milling, with up to four mills being counted in Ispaster in the decade of 1630. In the following century, one of the few windmills in all of Bizkaia was built on land belonging to the elizate, namely Aixeder Windmill dating from 1729, and which still stands today.

Present day

Today, the physiognomy of Ispaster is deeply marked by its legacy of centuries of continuous farming. Industrial activity can be seen in the likes of such companies as "Onduvisa" and the co-op "Lealde". Tourism, however, offers a new form of exploiting the abundant natural resources in the municipality.