Bank Indonesia (BI) said reserves increased to $117.2 billion at the end of November from $115.2 billion at the end of October. November reserves was equal to 6.5 months of imports, BI added.
The rupiah strengthened about 6 percent in November due to foreign investors' revived appetite for Indonesian assets, although the currency has weakened again recently.
Foreign investors bought 43.3 trillion rupiah ($2.99 billion) of fixed-income and equity assets during November, offsetting high domestic dollar demand to pay public debts, including for a maturing $1 billion sukuk, according to Satria Sambijantoro, Bahana Sekuritas economist.
"Latest FX reserves data should provide a reprieve for the rupiah, which reversed its strengths and depreciated by 1.6 percent this week," Sambijantoro said.
He predicted the rupiah will trade between 14,200-14,500 per dollar the rest of December.
The rupiah had been under pressure earlier in the year, trading at its lowest levels in 20 years when investors reduced holdings of emerging market assets due to rising U.S. interest rates and the U.S.-China trade war.
The central bank has raised interest rates six times by a total of 175 basis points since May to defend the currency.
(Reporting by Nilufar Rizki and Gayatri Suroyo; Editing by Richard Borsuk)