The company's performance worsened over the fourth quarter Christmas period – coinciding with gathering gloom over global growth and turmoil in financial markets.
All major regions except for Japan saw sales fall during the final three months – including Europe, which saw a "noteworthy decline" in France but growth in the UK.
Tiffany's said it expected earnings to fall in the first half of the current financial year and recover in the second half.
For 2015/16, annual worldwide same-store sales for the year were flat on the previous year but were 6% lower when translated into dollars thanks to the strength of the US currency.