"I believe we should welcome such a decision," Putin told a Shanghai Cooperation Organization summit on Friday.
"(It) is an important step towards the resolution of the Syrian crisis, this confirms the serious intention of our Syrian partners to follow this path."
Syria announced its full membership of the convention banning the use of chemical weapons on Thursday.
"Legally speaking Syria has become, starting today [Thursday], a full member of the (chemical weapons) convention," Syrian UN Ambassador Bashar al-Ja'afari told reporters in New York after submitting relevant documents to the United Nations on Thursday.
UN spokesman Farhan Haq told reporters the UN received a document Thursday from the Syrian government that concerns its accession to the 1993 Chemical Weapons Convention. He said the documentation is being studied.