Yehoshua Ossovetzki was born in Kiev, Ukraine. He acquired Hebrew and general education with an emphasis on the French language. Following the pogroms that occurred in South Russia in 1881, he came to Brody, Galicia. At that time, Karl Netter, stayed there as the envoy of "Alliance" who handled the Jewish emigration and Yehoshua Ossovetzki, who was fluent in Hebrew and French, helped him in establishing contacts with the immigrants.
Later on, he was brought to Eretz Israel by Karl Netter to be a teacher at the agricultural school "Mikvei Israel". Here he met the "Biluim" who were employed as farm hands, made friends with them and advocated them vis a vis the manager Hirsh who demonstrated an alienated attitude towards them and ridiculed their ideals.
In 1884, he was appointed to be the "Baron's Clerk" in Rishon Le zion. At that same year, a general meeting of farmers, which was convened in the settlement, decided to begin planting plenty of grapevines. The clerk Yehoshua Ossovetzki undertook to obtain the necessary budget from the Baron. Having managed that, he caused great enthusiasm among the farmers. He was also active in increasing the agricultural area of the settlement. In 1885, additional land, from the "Ayun Kara" was bought with his help. The land was divided between the new residents that settled in Rishon Le zion and the settlement grew and developed. In addition to that, he obtained from the Turkish government a license to build houses in the settlement and from the Baron he got the money for the construction works.
Yehoshua Ossovetzki should be credited for his plentiful activities in the redemption of land also in other areas outside Rishon Le zion. In Petach Tikva he saved with his endeavors a large piece of land bought from the Arabs; however, those refused to hand it over to the Jewish buyers. In the year 1887, he managed to transfer to the Jews' possession land in Southwest of Hedera. This land was purchased by the Baron's clerk for the sake of Jews who immigrated to Eretz Israel from Besarabia; an acquisition which encountered appeals by the Arab sellers. Thanks to the activities of Ossovetzki, the disputes were settled and on the ground was established Castina, that is, Beer Tuvia. Due to the licenses obtained for the construction, many houses were built in Beer Tuvia and Gedera. He pulled the people of Wadi Hanin (Ness Ziona) out of their economic troubles.
During his intensive activities, a severe conflict broke out between the farmers of Rishon Lezion and Ossovetzki i and the latters strongly demanded his removal from the settlement. They forbade him to enter the settlement's premises and threatened to kill him. When the Baron visited the settlement in 1887, the commotion was at its midst and Ossovetzki had to submit to the Baron a letter of resignation. The Baron, seemingly, accepted the resignation but immediately after that - located him in Petah Tikva and afterwards in Rosh Pina. In the Galilee he also continued his activities for the community. He saved Metulla's land which has been seized by the Druze and thereby salvaged the settlement from destruction.
Following this action he was appointed chief clerk of the Upper Galilee and did a lot for the stabilization of the settlements there. He was also interested in establishing settlements in Trans Jordan and following his advice the Baron bought land there. Later on, he was transferred to Beirut. There he also had to deal with matters concerning the acquisition of land and in creating good relations with Turkish high officials.
In 1900, after the Eretz Israel's settlements had been transferred to the "IKA" company, Yehoshua Ossovetzki left the country and settled in Paris, where he established a factory of music records. When he died, he was brought to burial there.