Background: Falls have been attributed to deterioration of dynamic walking balance. Accurate age-range determination of dynamic walking balance deterioration has yet to be elucidated. The purpose of this quasi-experimental study was to determine, by age/decade range, dynamic walking balance deterioration to provide a more accurate age range for interventional dynamic walking balance assessment and treatment. Methods: Participant demographic data were collected [age (years), gender, height (cm), body mass (kg), and body mass index (BMI) (kg•m-²)] on one hundred fifteen individuals between the ages of 20 and 80 years. Participants then completed a modified version of Rubenstein and colleagues' Fall Risk Questionnaire (mFRQ) and performed two trials of the ten step tandem walk test eyes open (TSTWT EO). Participant TSTWT EO scores were averaged and recorded as number of tandem walking steps, maximum of ten, prior to loss of balance. Results: A single factor ANOVA compared the effects of age, distributed per decade of life, on human dynamic walking balance. A statistically significant effect of age on TSTWT EO was found [F (1, 228) = 509.5053, p=4.8E-60]. Post hoc comparisons using two-sample t-tests indicated that the mean TSTWT EO score for the fourth decade of life group (30-39 years) (M=9.15, SD ± 0.65) was significantly different from the fifth decade of life group (40-49 years) (M=6.00, SD±1.61) (p=1.65E-10, d=2.57), after Bonferroni correction. No statistically significant difference between participants' capacity to successfully perform the TSTWT EO was found between the third and fourth life decades (20-29 and 30-39 years), fifth and sixth life decades (40-49 and 50-59 years), sixth and seventh life decades (50-59 and 60-69 years), nor seventh and eighth life decades (60-69 and 70-79). Conclusion: A statistically significant difference was found in the dynamic walking capacity of participants ranging in age from 20 to 80 years. Statistically significant dynamic walking balance deterioration was shown to occur during the fifth decade of life compared to the fourth decade of life, which indicated that balance assessment and mediation be considered during an individual's fifth decade of life, between the ages of 40 to 49 years.