Q. Can someone count the Omer in his mother tongue when it is not the language of the country where he is?

A. Biur Halocho (beginning of s. 62) in regards to reading Shema in other languages rules that although one complies, it is only if the people of that country know that particular idiom. If they don’t and it is only him and a few others that speak in that tongue, he does not comply. Contemporary Poskim debate as to how many people are needed for the Biur Halocho’s requirement. They maintain that as long as it is an established language spoken officially in at least one nation, one would comply, even if only a small minority understands the idiom in the location where he finds himself now. (Megodim Chadoshim – Brochos p. 153, Yabia Omer 5:12:4). Others (Safa Ne’emana 32,) compare it to the proverbial Seventy Languages that were used when the Torah was translated.

Horav Shlomo Miller’s Shlit”a opinion is that indeed, if for example, someone would count in Canada sefira in the Russian language he understands, he would comply with the mitzva as it is an established language.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a