Grändalssjön (Swedish for "Lake of Grändalen") is a small lake in Tyresö Municipality south-east of central Stockholm, Sweden.

Grändalssjön, one of the lakes within the Tyresån Lake System, empties in its eastern end into a southbound bay of lake Albysjön located north of it. Immediately north of Grändalssjön is the Raksta open-air area, and Övre kärret ("Upper Swamp"), a swampy lake, is located west of the lake. Two small cottages located nearby, Grändalen and Skansen, are part of Gamla Tyresö.

The lake is popular for bathing and fishing. Motorboats are not allowed on the lake. It is virtually unaffected by eutrophication and human activities. It consequently has moderate levels of nutrients.

The stock of crayfishes is undocumented, but fishing using a maximum of ten tools is allowed with a fishing license. Aquatic vegetation is dominated by Fragile Stonewort.

• Geography of Stockholm

• "Sjödjup och sjövolym" (PDF) (in Swedish). Swedish Meteorological and Hydrological Institute. 25 November 2009. p. 34. Retrieved 13 September 2020.
• "Vattenväxter i sjöarna på Södertörn och i angränsande områden samt uppbyggnad av en sjödatabas" (PDF) (in Swedish). Södertörnsekologerna. pp. Appendix 7, p 2. Archived from the original (PDF) on 2007-10-07. Retrieved 2008-02-23.
• "Tyresåns sjösystem" (in Swedish). Tyresö Municipality. Archived from the original on 2007-09-27. Retrieved 2008-03-02.
• "Vattenväxter" (in Swedish). Södertörnsekologerna. Archived from the original on 2007-10-07. Retrieved 2008-03-02.
• "Kräftfiskekort" (PDF) (in Swedish). Stockholm Municipality. p. 7. Retrieved 2008-03-02.