PC requirements

The Sims 3: Pets System Requirements

The Sims 3: Pets needs at least For XP 2.0 GHz P4 processor or equivalent / For Windows Vista and Windows 7 2.4 GHz, For XP 1 GB RAM / For Windows Vista and Windows 7 1.5 GB RAM. For NVIDIA ION™ computers, the game requires at least 2.0 GB RAM. and 128 MB Video Card with Pixel Shader 2.0 support graphics.

Verified Sources: Steam store listing
The Sims 3: Pets minimum and recommended PC specifications
Component Minimum
Operating system XP SP2 / Vista SP1 / Windows 7
Processor For XP 2.0 GHz P4 processor or equivalent / For Windows Vista and Windows 7 2.4 GHz
Memory For XP 1 GB RAM / For Windows Vista and Windows 7 1.5 GB RAM. For NVIDIA ION™ computers, the game requires at least 2.0 GB RAM.
Graphics 128 MB Video Card with Pixel Shader 2.0 support
Storage At least 3.5 GB of hard drive space with at least 1 GB additional space for custom content and saved games. 9.6 GB of hard drive
Not sure how your PC compares? Use the Can I Run It checker — pick your CPU and GPU and it tells you which column you land in.

Other platforms

The Sims 3: Pets is also available on these systems, where hardware is fixed and no per-PC check is needed:

Quick answers

Running The Sims 3: Pets on PC

Can my PC run The Sims 3: Pets?
Compare your CPU, GPU and RAM against the minimum column below. If your parts match or beat every minimum row, the game will launch — though you may need to lower settings. Matching the recommended column is what gets you 60fps at 1080p.
How much storage does The Sims 3: Pets need?
At least 3.5 GB of hard drive space with at least 1 GB additional space for custom content and saved games. 9.6 GB of hard drive