When is the best time to introduce my 4 month old chihuahua to my 4 year old German shepherd?

My german shepherd gets along well with average sized dogs, but he's a little energetic and I am concerned he may hurt the little pup.

After lunch

do this very slowly i have had experience very recently i got a chihuahua in February and he was only 9 weeks old and i had to introduce him to my shiz zu who is 3 years old so do it very carefully and at little times at once just hold your pup and just slowly have your other dog smell him and see how they react if your big dog starts to show his teeth back off asap so just do it slow and hopefully in no time they should get along but it will be difficult good luck

It`s not about the time. It`s the place. You need to introduce them in a neutral place. Meaning somewhere the two are both not used to or protective of like a friends yard, or the park. This is going to prevent fighting, even a friendly dog can attempt to deffend their home and territory. That is the biggest mistake owners make right there. Crate trainnig your new pup can help to, it gives your shepherd a break from the pup. Make sure your older dog gets LOTS of attention and treats, way more than usual.As far as hurting the pup in play, dont worry. It will probebly take the puppy whining a couple times to teach your shepherd what the chihuahua can handle. After that they should be fine.