A solitary try from Rachel Poolman was enough to give Wales their first win over Scotland in 10 years.
Uwic winger Poolman scored a minute before half-time and Wales managed to hold on for the remaining minutes.
The match had to be switched from Pontypridd to Treforst because of a frozen pitch at Sardis Road.
Wales lost heavily in their opening match against England last week, while the Scots were also out-played as they fell to France.
Wales: Non Evans (Tylorstown/Clifton); Louise Rickard (Saracens), Rhian Williams (Wasps), Clare Flowers (Tylorstown/Clifton), Rachel Poolman (UWIC); Naomi Thomas (Tylorstown/Clifton), Mellissa Berry (Worcester); Amy Broadstock (Llandaff North), Rhian Bowden (UWIC), Louise Horgan (Saracens), Liza Burgess (Tylorstown/Clifton), Claire Donovan (Saracens), Catrina Nicholas (Cardiff Quins), Jamie Kift (Tylorstown/Clifton), Kylie Wilson (Waterloo).
Replacements: Claire Horgan (Waterloo); Jenny Davies (Caernarfon); Dawn Mason (Richmond); Rachel Brown (Waterloo); Amy Day (UWIC); Elen Evans (Dolgellau); Philippa Tuttiett (UWIC).
Scotland: Lucy Millard (Murrayfield Wanderers); Chris Ovenden (Richmond), Rimma Petlevannaya (Murrayfield Wanderers), Rhona Shepherd (Murrayfield Wanderers), Veronica Fitzpatrick (RHC); Mary Pat Tierney (Watsonians), Paula Chalmers (Murrayfield Wanderers, capt); Karen Findlay (Richmond), Iona Frickleton (Watsonians), Gillian McCord (Watsonians), Lisa O┐Keefe (Richmond), Sarah Mee (Watsonians), Clare Muir (Richmond), Beth MacLeod (Murrayfield Wanderers), Donna Kennedy (Worcester).
Replacements: Victoria Wiseman (Richmond), Gail Russell (Hillhead/Jordanhill), Susie Brown (Hillhead/Jordanhill), Shona Watt (Supermarine), Lynsey Douglas (Murrayfield Wanderers), Katie Davies (Hillhead/Jordanhill), Melanie Christie (Blaydon).