There are two main ways to get yourself a Smeargle:
Smeargle via the Johto Safari Zone
The simplest way to get Smeargle is by catching one in the Johto Safari Zone. Let’s break this process down step-by-step.
Step 1: Going to Cianwood City
The Johto Safari Zone is located somewhere to the northwest of Cianwood City. If you’re not anywhere near the area, you can use the Fly to head there quickly. Once you’re there, head upwards and then to the left, where you should see a cave entrance and a sign that says “Entrance to the road for the Safari Zone.”
Step 2: At the Cliff Edge Gate
Head inside the cave, also known as Cliff Edge Gate. There’s a woman behind the counter who will give you the exact directions to the Safari Zone. Go to the left of the counter and then follow the path going down. This will take you to an exit leading to Route 47. Follow the path until you get to a cave entrance. Inside are two ladders. Take the one going up. This will lead you outside the cave again, this time to Route 48. Again, follow the path to the left going up. If you stick to this path, you’ll arrive at the Safari Zone Gate in no time at all.
Step 3: Inside the Safari Zone
Inside the Safari Zone, you have a 10% chance of encountering Smeargle just by walking through the grass in the Plains area from Morning to Day, or 04:00-19:59 in real-world time. The Smeargle you’ll find here will be Lv. 17 by default. However, once you’ve unlocked the ability to upgrade the Safari Zone through block objects, you can encounter Lv. 41 Smeargle. To do that, you need to have Forest block objects with a total score of 3. After adding these to the Plains area, you’ll have a 10% chance of finding and catching Lv. 41 Smeargle. Keep in mind that this can only happen after you’ve already received your National Pokédex from Professor Oak. Additionally, three hours of gameplay should’ve already passed after you’ve completed Baoba’s second challenge.
Smeargle via the Ruins of Alph
You can also find Smeargle in the Ruins of Alph, an area that’s accessible in both HG & SS. And unlike in the Safari Zone, you can catch Smeargle here at any time of the day.
Step 1: Going to Violet City
The quickest way to get to Ruins of Alph is to fly to Violet City. After arriving at Violet City, go down to Route 32. Just continue going down the path until you get to a dead-end and a sign that says “Union Cave ahead.”
Step 2: Entering Union Cave
Before entering Union Cave, make sure that you have a Pokémon who can use the HM Surf. If you don’t have one in your party, you can head inside the Pokémon Center just a few steps away. Go to your PC and get a Pokémon who knows Surf or can be taught Surf. Once you’re done, head over to Union Cave. Once inside, just follow the path going to the left until you encounter a set of stairs. Take those stairs to go down to the lower level.
Step 3: Traversing Union Cave
You should see a body of water near the stairs. Use Surf to get to the other side. Follow the path going up and then left. Once there, pick the path going up again and then head left once more. There should be a set of stairs going up. After taking the stairs, you should see another body of water where you can use Surf. At the end of it, there’s another set of stairs going up. This set of stairs will take you to an exit leading you right into the Ruins of Alph.
Step 4: Inside the Ruins of Alph
Walk into the structure in front of you, then once you’re inside it, keep going to your right. Then when you’re inside that structure you should walk down, leading you outside of the structure and into an open grassy area. Here, you should see a small grass patch. This is where you can catch wild Smeargle. You have a 10% chance of encountering your lovely Smeargle, and a 90% chance of encountering a wild Natu. So if you don’t encounter any Smeargle right away, don’t give up! You’re likely to go through at least nine Natu before even seeing one Smeargle.