How can a 22-year-old assault record affect my visa application?

If your wife is a Portuguese national, or a national of another European Union Member State who holds a Registration Certificate or Permanent Residence Certificate in Portugal, you may be eligible to apply for a residence permit under Article 15 of Law No. 37/2006.
Please note that, within the scope of such an application, the competent authorities may request and assess information relating to the applicant’s criminal record. The final decision on the application remains at AIMA’s discretion, following its assessment of all relevant circumstances and supporting documentation.
However, if your wife is a third-country national holding a Portuguese residence permit, the applicable legal framework is Law No. 23/2007 of 4 July. Under Article 52(3) of this law, a residence visa may be refused to third-country nationals who have been convicted of an offence punishable under Portuguese law by a custodial sentence of more than one year, regardless of whether the sentence was effectively served or suspended.
With regard to the offense of assault, Portuguese criminal law distinguishes between different categories of assault offenses, ranging from simple assault to aggravated assault, depending on the specific circumstances and severity of the conduct. Therefore, a proper assessment would require a detailed analysis of the nature of the offense for which you were convicted and its equivalent classification under Portuguese law.
In this context, your previous conviction may potentially constitute grounds for refusal.
That said, each case is assessed on its individual merits, and factors such as the time elapsed since the offense, your conduct since the conviction, and evidence of rehabilitation may be relevant to the overall assessment.
Given the circumstances, we would recommend obtaining specific legal advice before proceeding with any application, so that your situation can be properly evaluated in light of the applicable legal framework.