Cleffa locations — where to catch

In Lumiose City (Legends: Z-A)

• Bleu Sector 4 — Walk
• Jaune Sector 11 — Walk
• Magenta Sector 1 — Walk
• Rouge Sector 5 — Walk
• Vert Sector 3 — Walk
• Wild Zone 19 — Walk

In Kitakami (Scarlet & Violet – The Teal Mask)

• Infernal Pass — Walk
• Oni Mountain — Walk
• Reveler's Road — Walk

In Hisui (Legends: Arceus)

• Fabled Spring — Walk

In Sinnoh (Diamond, Pearl & Platinum)

• Mt. Coronet — Walk
• Trophy Garden — Walk

In Johto & Kanto (Gold, Silver & Crystal)

• Route 34 — Gift

Other games (5)

• Brilliant Diamond / Shining Pearl (Gen 8): Trophy Garden
• Sword / Shield — The Isle of Armor (Gen 8): Ballimere Lake, Fields of Honor, Forest of Focus, Frigid Sea, Frostpoint Field, Giant's Bed, Insular Sea, Snowslide Slope, Soothing Wetlands
• Sword / Shield (Gen 8): Hammerlocke Hills, Rolling Fields
• Ultra Sun / Ultra Moon (Gen 7): Mount Hokulani
• Sun / Moon (Gen 7): Mount Hokulani

Cleffa — full Pokédex entry