How to Install a Cat Door | A Straightforward Walkthrough

Installing a cat door means cutting a hole in your door and bolting two frames together around it—a job most DIYers finish in about an hour.

If you’ve ever watched your cat scratch at a closed door and wished they could come and go without you playing doorman, a cat door is the fix. This guide walks through the standard installation method used by PetSafe, the most common brand, so you can measure, cut, and mount the door with confidence—no prior carpentry skills required.

What You’ll Need Before You Start

The core of any cat door installation is simple: you remove the door, cut an opening using the included template, and fasten the interior and exterior frames together through the cut. Before you begin, gather these essentials:

• A jigsaw with a fine-tooth blade for clean cuts
• A drill with the bit sizes listed in your kit’s instructions
• A pencil and the cardboard or paper template that ships with your cat door
• A screwdriver, plus a level and tape measure
• A caulk gun and weatherproof exterior caulk for sealing

If your door is hollow-core rather than solid wood, prepare for one key difference: over-torquing the screws can crack the interior frame. Many hollow doors only need two fasteners instead of four, so snug them gently.

Measuring and Marking the Correct Height

The most common mistake happens before the saw ever touches the door: cutting at the wrong height. A cat door must align with your cat’s natural stride, not their head height.

This positions the bottom of the opening at belly level so your cat steps through comfortably rather than crouching or leaping.

A helpful tip for anyone installing a cat door: hold the template against the door at the marked height, use the level to make sure it’s straight, and trace the edges with your pencil before drilling. A lopsided opening makes the frame look crooked and can cause the flap to bind.

Cutting the Opening and Fitting the Frames

Once your marks are in place, the cutting process follows a consistent order. The pilot holes give your jigsaw blade a place to start and keep the cut clean.

After the corner holes are drilled, cut along your traced lines with the jigsaw. Go slowly and keep the saw perpendicular to the door face for a straight edge. The manufacturer’s metal-core door guide adds one critical step for heavier doors: remove the door from its hinges and lay it flat on a raised, stable surface like sawhorses, then clamp it down before cutting. This supports the door’s weight and prevents the wood from splintering as the blade exits.

With the hole cut, assembly is straightforward. Position the interior frame on the inside face of the door, place the exterior frame on the other side, and insert screws through the exterior frame into the interior one. PetSafe’s guides note that you should pick screw lengths based on your door’s actual thickness—a thinner hollow door needs shorter screws than a thick solid one. Their standard install sequence has you secure the middle frame, then the exterior, then the interior, tightening gently to avoid cracking the frames on hollow-core doors.

Before you rehang the door, confirm the flap swings freely through its full range and returns to the closed position without sticking. If it catches, loosen the screws a quarter-turn and adjust the frame alignment.

Sealing and Final Touches for Weather Resistance

Your last step before rehanging the door is making the installation weatherproof. Run a smooth bead along the seam between the frame and the door face, then smooth it with a damp finger. This keeps drafts, rain, and insects from sneaking in around the edges.

Rehang the door, and you’re done. For more advanced setups, the manufacturer’s metal-core door guide covers adapter-plate installations for steel or metal-core doors, which use a different template and mounting method than standard wooden doors.

If you’re weighing whether to buy a basic flap versus an automatic model that only lets your own cat through, our roundup of the best auto cat doors breaks down the smarter options, including microchip and RFID models. These use the same installation method described above but add a locking mechanism that keeps strays out while your cat comes and goes freely.