I understand your concerns, but it’s important to approach the situation with the right mindset.

If you place all the responsibility for a successful outcome on the dogs themselves, then there is reason to worry. However, if you are willing to put in the necessary work and effort, things should turn out fine.

So, what does that entail?

First and foremost, have an open and honest conversation with your partner about your concerns. Emphasize the importance of adopting a large dog with no history of aggression and preferably a background of getting along well with dogs of all sizes, for the safety of everyone involved.

Make it clear that larger dogs often require more exercise, and meeting their exercise needs is crucial for positive interactions.

Simultaneously, ensure that your Chihuahua receives proper obedience training, exercise, and mental stimulation. This not only sets both dogs up for success but also reinforces the idea that they need to listen and respect each other even in the presence of a new dog.

Educate yourself on how to introduce two dogs properly. Take your time and closely monitor the initial interactions, especially considering the significant size difference and the fact that the dogs are unfamiliar with each other. Learn to recognize canine body language so you can understand if and when either dog needs a break.

Seek advice from the agency or rescue organization you adopt from regarding their recommendations, and make sure to follow them. Avoid allowing rough play or harassment between the dogs. Both dogs need to learn the household rules in relation to each other and the people in the home.

Even after you trust them around each other, commit to providing proper supervision if either dog is ill, overly excited, triggered by fear, or in a new situation where their reactions are uncertain.

Lastly, commit to working with both dogs so they develop good manners not only with each other but also with others. Ensure that you can meet the physical and mental needs of both dogs as they age. If either dog experiences health issues, consider the size difference when managing their interactions and exercise.

If you can dedicate yourself to all of these steps, you should be fine. Additionally, it may be helpful to seek guidance from a professional trainer or behaviorist before the adoption to have support readily available when needed.

Good luck!